[PATCH 0/4] Fixes for SEV-SNP CC blob and CPUID table handling

[PATCH 0/4] Fixes for SEV-SNP CC blob and CPUID table handling

[Roth, Michael]

Here are a number of fixes related to OVMF handling of the SEV-SNP
Confidential Computing blob and CPUID table.

Patch #1 is a fix for recently-reported issue that can cause
significant problems with some SEV-SNP guest operating systems.
Please consider applying this patch directly if the other
patches in this series are held up for any reason.

Patches 2-4 are minor changes for things that aren't currently
triggered in practice, but make OVMF's SEV-SNP implementation more
robust for different build/hypervisor environments in the future.
Patch #2 was submitted previously, but refreshed here to apply
cleanly on top of Patch #1, with no other functional changes since
the initial review.

----------------------------------------------------------------
Michael Roth (4):
      OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory
      OvmfPkg/AmdSevDxe: Update ConfidentialComputing blob struct definition
      OvmfPkg/CcExitLib: Fix SEV-SNP XSave area size calculation
      OvmfPkg/CcExitLib: Use documented XSave area base size for SEV-SNP

 OvmfPkg/AmdSevDxe/AmdSevDxe.c                          | 64 ++++++++++++++++++++++++++++++++++----------
 OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h |  6 +++--
 OvmfPkg/Library/CcExitLib/CcExitVcHandler.c            | 13 ++++-----
 3 files changed, 59 insertions(+), 24 deletions(-)

[PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory

[Roth, Michael]

The SEV-SNP Confidential Computing blob contains metadata that should
remain accessible for the life of the guest. Allocate it as
EfiACPIReclaimMemory to ensure the memory isn't overwritten by the guest
operating system later.

Reported-by: Dov Murik <dovmurik@linux.ibm.com>
Suggested-by: Dov Murik <dovmurik@linux.ibm.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
 OvmfPkg/AmdSevDxe/AmdSevDxe.c | 62 +++++++++++++++++++++++++++--------
 1 file changed, 48 insertions(+), 14 deletions(-)

diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
index 662d3c4ccb..8dfda961d7 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
@@ -21,15 +21,36 @@
 #include <Guid/ConfidentialComputingSevSnpBlob.h>
 #include <Library/PcdLib.h>
 
-STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  mSnpBootDxeTable = {
-  SIGNATURE_32 ('A',                                    'M', 'D', 'E'),
-  1,
-  0,
-  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase),
-  FixedPcdGet32 (PcdOvmfSnpSecretsSize),
-  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase),
-  FixedPcdGet32 (PcdOvmfCpuidSize),
-};
+STATIC
+EFI_STATUS
+AllocateConfidentialComputingBlob (
+  OUT CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  **CcBlobPtr
+  )
+{
+  EFI_STATUS                                Status;
+  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *CcBlob;
+
+  Status = gBS->AllocatePool (
+                  EfiACPIReclaimMemory,
+                  sizeof (CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION),
+                  (VOID **)&CcBlob
+                  );
+  if (EFI_ERROR (Status)) {
+    return Status;
+  }
+
+  CcBlob->Header                 = SIGNATURE_32 ('A', 'M', 'D', 'E');
+  CcBlob->Version                = 1;
+  CcBlob->Reserved1              = 0;
+  CcBlob->SecretsPhysicalAddress = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase);
+  CcBlob->SecretsSize            = FixedPcdGet32 (PcdOvmfSnpSecretsSize);
+  CcBlob->CpuidPhysicalAddress   = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase);
+  CcBlob->CpuidLSize             = FixedPcdGet32 (PcdOvmfCpuidSize);
+
+  *CcBlobPtr = CcBlob;
+
+  return EFI_SUCCESS;
+}
 
 EFI_STATUS
 EFIAPI
@@ -38,10 +59,11 @@ AmdSevDxeEntryPoint (
   IN EFI_SYSTEM_TABLE  *SystemTable
   )
 {
-  EFI_STATUS                       Status;
-  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *AllDescMap;
-  UINTN                            NumEntries;
-  UINTN                            Index;
+  EFI_STATUS                                Status;
+  EFI_GCD_MEMORY_SPACE_DESCRIPTOR           *AllDescMap;
+  UINTN                                     NumEntries;
+  UINTN                                     Index;
+  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *SnpBootDxeTable;
 
   //
   // Do nothing when SEV is not enabled
@@ -147,6 +169,18 @@ AmdSevDxeEntryPoint (
     }
   }
 
+  Status = AllocateConfidentialComputingBlob (&SnpBootDxeTable);
+  if (EFI_ERROR (Status)) {
+    DEBUG ((
+      DEBUG_ERROR,
+      "%a: AllocateConfidentialComputingBlob(): %r\n",
+      __FUNCTION__,
+      Status
+      ));
+    ASSERT (FALSE);
+    CpuDeadLoop ();
+  }
+
   //
   // If its SEV-SNP active guest then install the CONFIDENTIAL_COMPUTING_SEV_SNP_BLOB.
   // It contains the location for both the Secrets and CPUID page.
@@ -154,7 +188,7 @@ AmdSevDxeEntryPoint (
   if (MemEncryptSevSnpIsEnabled ()) {
     return gBS->InstallConfigurationTable (
                   &gConfidentialComputingSevSnpBlobGuid,
-                  &mSnpBootDxeTable
+                  SnpBootDxeTable
                   );
   }
 
-- 
2.25.1

[PATCH 2/4] OvmfPkg/AmdSevDxe: Update ConfidentialComputing blob struct definition

[Roth, Michael]

The Confidential Computing blob defined here is intended to match the
definition defined by linux guest kernel. Previously, both definitions
relied on natural alignment, but that relies on both OVMF and kernel
being compiled as 64-bit. While there aren't currently any plans to
enable SNP support for 32-bit compilations, the kernel definition has
since been updated to use explicit padding/reserved fields to avoid
this dependency. Update OVMF to match that definition.

While at it, also fix up the Reserved fields to match the numbering
used in the kernel.

No functional changes (for currently-supported environments, at least).

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
 OvmfPkg/AmdSevDxe/AmdSevDxe.c                          | 4 +++-
 OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h | 6 ++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
index 8dfda961d7..00bb6e5d96 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
@@ -41,11 +41,13 @@ AllocateConfidentialComputingBlob (
 
   CcBlob->Header                 = SIGNATURE_32 ('A', 'M', 'D', 'E');
   CcBlob->Version                = 1;
-  CcBlob->Reserved1              = 0;
+  CcBlob->Reserved               = 0;
   CcBlob->SecretsPhysicalAddress = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase);
   CcBlob->SecretsSize            = FixedPcdGet32 (PcdOvmfSnpSecretsSize);
+  CcBlob->Reserved1              = 0;
   CcBlob->CpuidPhysicalAddress   = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase);
   CcBlob->CpuidLSize             = FixedPcdGet32 (PcdOvmfCpuidSize);
+  CcBlob->Reserved2              = 0;
 
   *CcBlobPtr = CcBlob;
 
diff --git a/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h b/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
index b328310fd0..83620e31b8 100644
--- a/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
+++ b/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
@@ -18,14 +18,16 @@
     { 0x85, 0x54, 0x93, 0xd7, 0x77, 0x91, 0x2d, 0x42 }, \
   }
 
-typedef struct {
+typedef PACKED struct {
   UINT32    Header;
   UINT16    Version;
-  UINT16    Reserved1;
+  UINT16    Reserved;
   UINT64    SecretsPhysicalAddress;
   UINT32    SecretsSize;
+  UINT32    Reserved1;
   UINT64    CpuidPhysicalAddress;
   UINT32    CpuidLSize;
+  UINT32    Reserved2;
 } CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION;
 
 extern EFI_GUID  gConfidentialComputingSevSnpBlobGuid;
-- 
2.25.1

[PATCH 3/4] OvmfPkg/CcExitLib: Fix SEV-SNP XSave area size calculation

[Roth, Michael]

CPUID leaf 0xD sub-leafs 0x0 and 0x1 contain cumulative sizes for the
enabled XSave areas. Those sizes are calculated by tallying up all the
other sub-leafs that contain per-area size information for XSave areas
that are currently enabled in XCr0/XSS. The current check has the logic
inverted. Fix that.

This doesn't seem to cause problems currently, but could in the future
if OVMF made more extensive use of XSave areas. It was noticed while
implementing SNP-related tests for KVM Unit Tests, which re-uses the
OVMF #VC handler in some cases.

Reported-by: Pavan Kumar Paluri <papaluri@amd.com>
Cc: Pavan Kumar Paluri <papaluri@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
 OvmfPkg/Library/CcExitLib/CcExitVcHandler.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
index 985e547977..cd117d5a31 100644
--- a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
+++ b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
@@ -1678,9 +1678,7 @@ GetCpuidXSaveSize (
   for (Idx = 0; Idx < CpuidInfo->Count; Idx++) {
     SEV_SNP_CPUID_FUNCTION  *CpuidFn = &CpuidInfo->function[Idx];
 
-    if (!((CpuidFn->EaxIn == 0xD) &&
-          ((CpuidFn->EcxIn == 0) || (CpuidFn->EcxIn == 1))))
-    {
+    if (!((CpuidFn->EaxIn == 0xD) && (CpuidFn->EcxIn > 1))) {
       continue;
     }
 
-- 
2.25.1

[PATCH 4/4] OvmfPkg/CcExitLib: Use documented XSave area base size for SEV-SNP

[Roth, Michael]

Currently OVMF tries to rely on the base size advertised via the CPUID
table entries corresponding to leaf 0xD, sub-leafs 0x0/0x1. This will
generally work for KVM guests, but might not for other SEV-SNP
hypervisor implementations. Make the handling more robust by simply
using the base area size documented by the APM.

Signed-off-by: Michael Roth <michael.roth@amd.com>
---
 OvmfPkg/Library/CcExitLib/CcExitVcHandler.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
index cd117d5a31..f985dcff8d 100644
--- a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
+++ b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
@@ -1647,8 +1647,6 @@ SnpEnabled (
 
   @param[in]      XFeaturesEnabled  Bit-mask of enabled XSAVE features/areas as
                                     indicated by XCR0/MSR_IA32_XSS bits
-  @param[in]      XSaveBaseSize     Base/legacy XSAVE area size (e.g. when
-                                    XCR0 is 1)
   @param[in, out] XSaveSize         Pointer to storage for calculated XSAVE area
                                     size
   @param[in]      Compacted         Whether or not the calculation is for the
@@ -1663,7 +1661,6 @@ STATIC
 BOOLEAN
 GetCpuidXSaveSize (
   IN     UINT64   XFeaturesEnabled,
-  IN     UINT32   XSaveBaseSize,
   IN OUT UINT32   *XSaveSize,
   IN     BOOLEAN  Compacted
   )
@@ -1672,7 +1669,10 @@ GetCpuidXSaveSize (
   UINT64              XFeaturesFound = 0;
   UINT32              Idx;
 
-  *XSaveSize = XSaveBaseSize;
+  //
+  // The base/legacy XSave size is documented to be 0x240 in the APM.
+  //
+  *XSaveSize = 0x240;
   CpuidInfo  = (SEV_SNP_CPUID_INFO *)(UINT64)PcdGet32 (PcdOvmfCpuidBase);
 
   for (Idx = 0; Idx < CpuidInfo->Count; Idx++) {
@@ -1888,7 +1888,6 @@ GetCpuidFw (
 
     if (!GetCpuidXSaveSize (
            XCr0 | XssMsr.Uint64,
-           *Ebx,
            &XSaveSize,
            Compacted
            ))
-- 
2.25.1

Re: [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory

[Lendacky, Thomas]

On 12/21/22 10:06, Michael Roth wrote:
> The SEV-SNP Confidential Computing blob contains metadata that should
> remain accessible for the life of the guest. Allocate it as
> EfiACPIReclaimMemory to ensure the memory isn't overwritten by the guest
> operating system later.
> 
> Reported-by: Dov Murik <dovmurik@linux.ibm.com>
> Suggested-by: Dov Murik <dovmurik@linux.ibm.com>
> Signed-off-by: Michael Roth <michael.roth@amd.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>   OvmfPkg/AmdSevDxe/AmdSevDxe.c | 62 +++++++++++++++++++++++++++--------
>   1 file changed, 48 insertions(+), 14 deletions(-)
> 
> diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> index 662d3c4ccb..8dfda961d7 100644
> --- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> +++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> @@ -21,15 +21,36 @@
>   #include <Guid/ConfidentialComputingSevSnpBlob.h>
>   #include <Library/PcdLib.h>
>   
> -STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  mSnpBootDxeTable = {
> -  SIGNATURE_32 ('A',                                    'M', 'D', 'E'),
> -  1,
> -  0,
> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase),
> -  FixedPcdGet32 (PcdOvmfSnpSecretsSize),
> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase),
> -  FixedPcdGet32 (PcdOvmfCpuidSize),
> -};
> +STATIC
> +EFI_STATUS
> +AllocateConfidentialComputingBlob (
> +  OUT CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  **CcBlobPtr
> +  )
> +{
> +  EFI_STATUS                                Status;
> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *CcBlob;
> +
> +  Status = gBS->AllocatePool (
> +                  EfiACPIReclaimMemory,
> +                  sizeof (CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION),
> +                  (VOID **)&CcBlob
> +                  );
> +  if (EFI_ERROR (Status)) {
> +    return Status;
> +  }
> +
> +  CcBlob->Header                 = SIGNATURE_32 ('A', 'M', 'D', 'E');
> +  CcBlob->Version                = 1;
> +  CcBlob->Reserved1              = 0;
> +  CcBlob->SecretsPhysicalAddress = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase);
> +  CcBlob->SecretsSize            = FixedPcdGet32 (PcdOvmfSnpSecretsSize);
> +  CcBlob->CpuidPhysicalAddress   = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase);
> +  CcBlob->CpuidLSize             = FixedPcdGet32 (PcdOvmfCpuidSize);
> +
> +  *CcBlobPtr = CcBlob;
> +
> +  return EFI_SUCCESS;
> +}
>   
>   EFI_STATUS
>   EFIAPI
> @@ -38,10 +59,11 @@ AmdSevDxeEntryPoint (
>     IN EFI_SYSTEM_TABLE  *SystemTable
>     )
>   {
> -  EFI_STATUS                       Status;
> -  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *AllDescMap;
> -  UINTN                            NumEntries;
> -  UINTN                            Index;
> +  EFI_STATUS                                Status;
> +  EFI_GCD_MEMORY_SPACE_DESCRIPTOR           *AllDescMap;
> +  UINTN                                     NumEntries;
> +  UINTN                                     Index;
> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *SnpBootDxeTable;
>   
>     //
>     // Do nothing when SEV is not enabled
> @@ -147,6 +169,18 @@ AmdSevDxeEntryPoint (
>       }
>     }
>   
> +  Status = AllocateConfidentialComputingBlob (&SnpBootDxeTable);
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((
> +      DEBUG_ERROR,
> +      "%a: AllocateConfidentialComputingBlob(): %r\n",
> +      __FUNCTION__,
> +      Status
> +      ));
> +    ASSERT (FALSE);
> +    CpuDeadLoop ();
> +  }
> +
>     //
>     // If its SEV-SNP active guest then install the CONFIDENTIAL_COMPUTING_SEV_SNP_BLOB.
>     // It contains the location for both the Secrets and CPUID page.
> @@ -154,7 +188,7 @@ AmdSevDxeEntryPoint (
>     if (MemEncryptSevSnpIsEnabled ()) {
>       return gBS->InstallConfigurationTable (
>                     &gConfidentialComputingSevSnpBlobGuid,
> -                  &mSnpBootDxeTable
> +                  SnpBootDxeTable
>                     );
>     }
>   

Re: [PATCH 3/4] OvmfPkg/CcExitLib: Fix SEV-SNP XSave area size calculation

[Lendacky, Thomas]

On 12/21/22 10:06, Michael Roth wrote:
> CPUID leaf 0xD sub-leafs 0x0 and 0x1 contain cumulative sizes for the
> enabled XSave areas. Those sizes are calculated by tallying up all the
> other sub-leafs that contain per-area size information for XSave areas
> that are currently enabled in XCr0/XSS. The current check has the logic
> inverted. Fix that.
> 
> This doesn't seem to cause problems currently, but could in the future
> if OVMF made more extensive use of XSave areas. It was noticed while
> implementing SNP-related tests for KVM Unit Tests, which re-uses the
> OVMF #VC handler in some cases.
> 
> Reported-by: Pavan Kumar Paluri <papaluri@amd.com>
> Cc: Pavan Kumar Paluri <papaluri@amd.com>
> Signed-off-by: Michael Roth <michael.roth@amd.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>   OvmfPkg/Library/CcExitLib/CcExitVcHandler.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> index 985e547977..cd117d5a31 100644
> --- a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> +++ b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> @@ -1678,9 +1678,7 @@ GetCpuidXSaveSize (
>     for (Idx = 0; Idx < CpuidInfo->Count; Idx++) {
>       SEV_SNP_CPUID_FUNCTION  *CpuidFn = &CpuidInfo->function[Idx];
>   
> -    if (!((CpuidFn->EaxIn == 0xD) &&
> -          ((CpuidFn->EcxIn == 0) || (CpuidFn->EcxIn == 1))))
> -    {
> +    if (!((CpuidFn->EaxIn == 0xD) && (CpuidFn->EcxIn > 1))) {
>         continue;
>       }
>   

Re: [PATCH 4/4] OvmfPkg/CcExitLib: Use documented XSave area base size for SEV-SNP

[Lendacky, Thomas]

On 12/21/22 10:06, Michael Roth wrote:
> Currently OVMF tries to rely on the base size advertised via the CPUID
> table entries corresponding to leaf 0xD, sub-leafs 0x0/0x1. This will
> generally work for KVM guests, but might not for other SEV-SNP
> hypervisor implementations. Make the handling more robust by simply
> using the base area size documented by the APM.
> 
> Signed-off-by: Michael Roth <michael.roth@amd.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>   OvmfPkg/Library/CcExitLib/CcExitVcHandler.c | 9 ++++-----
>   1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> index cd117d5a31..f985dcff8d 100644
> --- a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> +++ b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> @@ -1647,8 +1647,6 @@ SnpEnabled (
>   
>     @param[in]      XFeaturesEnabled  Bit-mask of enabled XSAVE features/areas as
>                                       indicated by XCR0/MSR_IA32_XSS bits
> -  @param[in]      XSaveBaseSize     Base/legacy XSAVE area size (e.g. when
> -                                    XCR0 is 1)
>     @param[in, out] XSaveSize         Pointer to storage for calculated XSAVE area
>                                       size
>     @param[in]      Compacted         Whether or not the calculation is for the
> @@ -1663,7 +1661,6 @@ STATIC
>   BOOLEAN
>   GetCpuidXSaveSize (
>     IN     UINT64   XFeaturesEnabled,
> -  IN     UINT32   XSaveBaseSize,
>     IN OUT UINT32   *XSaveSize,
>     IN     BOOLEAN  Compacted
>     )
> @@ -1672,7 +1669,10 @@ GetCpuidXSaveSize (
>     UINT64              XFeaturesFound = 0;
>     UINT32              Idx;
>   
> -  *XSaveSize = XSaveBaseSize;
> +  //
> +  // The base/legacy XSave size is documented to be 0x240 in the APM.
> +  //
> +  *XSaveSize = 0x240;
>     CpuidInfo  = (SEV_SNP_CPUID_INFO *)(UINT64)PcdGet32 (PcdOvmfCpuidBase);
>   
>     for (Idx = 0; Idx < CpuidInfo->Count; Idx++) {
> @@ -1888,7 +1888,6 @@ GetCpuidFw (
>   
>       if (!GetCpuidXSaveSize (
>              XCr0 | XssMsr.Uint64,
> -           *Ebx,
>              &XSaveSize,
>              Compacted
>              ))

Re: [PATCH 0/4] Fixes for SEV-SNP CC blob and CPUID table handling

[Roth, Michael]

On Wed, Dec 21, 2022 at 10:06:47AM -0600, Michael Roth wrote:
> Here are a number of fixes related to OVMF handling of the SEV-SNP
> Confidential Computing blob and CPUID table.
> 
> Patch #1 is a fix for recently-reported issue that can cause
> significant problems with some SEV-SNP guest operating systems.
> Please consider applying this patch directly if the other
> patches in this series are held up for any reason.
> 
> Patches 2-4 are minor changes for things that aren't currently
> triggered in practice, but make OVMF's SEV-SNP implementation more
> robust for different build/hypervisor environments in the future.
> Patch #2 was submitted previously, but refreshed here to apply
> cleanly on top of Patch #1, with no other functional changes since
> the initial review.
> 
> ----------------------------------------------------------------
> Michael Roth (4):
>       OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory
>       OvmfPkg/AmdSevDxe: Update ConfidentialComputing blob struct definition
>       OvmfPkg/CcExitLib: Fix SEV-SNP XSave area size calculation
>       OvmfPkg/CcExitLib: Use documented XSave area base size for SEV-SNP

Adding some Cc's from Maintainers.txt that I should have included
originally:

  Ard Biesheuvel <ardb+tianocore@kernel.org>
  Jiewen Yao <jiewen.yao@intel.com>
  Gerd Hoffmann <kraxel@redhat.com>
  Erdem Aktas <erdemaktas@google.com>
  James Bottomley <jejb@linux.ibm.com>
  Min Xu <min.m.xu@intel.com>

Thanks,

Mike

> 
>  OvmfPkg/AmdSevDxe/AmdSevDxe.c                          | 64 ++++++++++++++++++++++++++++++++++----------
>  OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h |  6 +++--
>  OvmfPkg/Library/CcExitLib/CcExitVcHandler.c            | 13 ++++-----
>  3 files changed, 59 insertions(+), 24 deletions(-)
> 
> 

Re: [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory

[Dov Murik]

Thanks Mike for fixing this.

On 21/12/2022 18:06, Michael Roth wrote:
> The SEV-SNP Confidential Computing blob contains metadata that should
> remain accessible for the life of the guest. Allocate it as
> EfiACPIReclaimMemory to ensure the memory isn't overwritten by the guest
> operating system later.
> 
> Reported-by: Dov Murik <dovmurik@linux.ibm.com>
> Suggested-by: Dov Murik <dovmurik@linux.ibm.com>
> Signed-off-by: Michael Roth <michael.roth@amd.com>

Reviewed-by: Dov Murik <dovmurik@linux.ibm.com>


> ---
>  OvmfPkg/AmdSevDxe/AmdSevDxe.c | 62 +++++++++++++++++++++++++++--------
>  1 file changed, 48 insertions(+), 14 deletions(-)
> 
> diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> index 662d3c4ccb..8dfda961d7 100644
> --- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> +++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> @@ -21,15 +21,36 @@
>  #include <Guid/ConfidentialComputingSevSnpBlob.h>
> 
>  #include <Library/PcdLib.h>
> 
>  
> 
> -STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  mSnpBootDxeTable = {
> 
> -  SIGNATURE_32 ('A',                                    'M', 'D', 'E'),
> 
> -  1,
> 
> -  0,
> 
> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase),
> 
> -  FixedPcdGet32 (PcdOvmfSnpSecretsSize),
> 
> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase),
> 
> -  FixedPcdGet32 (PcdOvmfCpuidSize),
> 
> -};
> 
> +STATIC
> 
> +EFI_STATUS
> 
> +AllocateConfidentialComputingBlob (
> 
> +  OUT CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  **CcBlobPtr
> 
> +  )
> 
> +{
> 
> +  EFI_STATUS                                Status;
> 
> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *CcBlob;
> 
> +
> 
> +  Status = gBS->AllocatePool (
> 
> +                  EfiACPIReclaimMemory,
> 
> +                  sizeof (CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION),
> 
> +                  (VOID **)&CcBlob
> 
> +                  );
> 
> +  if (EFI_ERROR (Status)) {
> 
> +    return Status;
> 
> +  }
> 
> +
> 
> +  CcBlob->Header                 = SIGNATURE_32 ('A', 'M', 'D', 'E');
> 
> +  CcBlob->Version                = 1;
> 
> +  CcBlob->Reserved1              = 0;
> 
> +  CcBlob->SecretsPhysicalAddress = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase);
> 
> +  CcBlob->SecretsSize            = FixedPcdGet32 (PcdOvmfSnpSecretsSize);
> 
> +  CcBlob->CpuidPhysicalAddress   = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase);
> 
> +  CcBlob->CpuidLSize             = FixedPcdGet32 (PcdOvmfCpuidSize);
> 
> +
> 
> +  *CcBlobPtr = CcBlob;
> 
> +
> 
> +  return EFI_SUCCESS;
> 
> +}
> 
>  
> 
>  EFI_STATUS
> 
>  EFIAPI
> 
> @@ -38,10 +59,11 @@ AmdSevDxeEntryPoint (
>    IN EFI_SYSTEM_TABLE  *SystemTable
> 
>    )
> 
>  {
> 
> -  EFI_STATUS                       Status;
> 
> -  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *AllDescMap;
> 
> -  UINTN                            NumEntries;
> 
> -  UINTN                            Index;
> 
> +  EFI_STATUS                                Status;
> 
> +  EFI_GCD_MEMORY_SPACE_DESCRIPTOR           *AllDescMap;
> 
> +  UINTN                                     NumEntries;
> 
> +  UINTN                                     Index;
> 
> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *SnpBootDxeTable;
> 
>  
> 
>    //
> 
>    // Do nothing when SEV is not enabled
> 
> @@ -147,6 +169,18 @@ AmdSevDxeEntryPoint (
>      }
> 
>    }
> 
>  
> 
> +  Status = AllocateConfidentialComputingBlob (&SnpBootDxeTable);
> 
> +  if (EFI_ERROR (Status)) {
> 
> +    DEBUG ((
> 
> +      DEBUG_ERROR,
> 
> +      "%a: AllocateConfidentialComputingBlob(): %r\n",
> 
> +      __FUNCTION__,
> 
> +      Status
> 
> +      ));
> 
> +    ASSERT (FALSE);
> 
> +    CpuDeadLoop ();
> 
> +  }
> 
> +
> 
>    //
> 
>    // If its SEV-SNP active guest then install the CONFIDENTIAL_COMPUTING_SEV_SNP_BLOB.
> 
>    // It contains the location for both the Secrets and CPUID page.
> 
> @@ -154,7 +188,7 @@ AmdSevDxeEntryPoint (
>    if (MemEncryptSevSnpIsEnabled ()) {
> 
>      return gBS->InstallConfigurationTable (
> 
>                    &gConfidentialComputingSevSnpBlobGuid,
> 
> -                  &mSnpBootDxeTable
> 
> +                  SnpBootDxeTable
> 
>                    );
> 
>    }
> 
>  
> 

Re: [edk2-devel] [PATCH 3/4] OvmfPkg/CcExitLib: Fix SEV-SNP XSave area size calculation

[Yao, Jiewen]

Acked-by: Jiewen Yao <jiewen.yao@intel.com>

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Roth,
> Michael via groups.io
> Sent: Thursday, December 22, 2022 12:07 AM
> To: devel@edk2.groups.io
> Cc: Tom Lendacky <thomas.lendacky@amd.com>; Ni, Ray
> <ray.ni@intel.com>; Pavan Kumar Paluri <papaluri@amd.com>
> Subject: [edk2-devel] [PATCH 3/4] OvmfPkg/CcExitLib: Fix SEV-SNP XSave area
> size calculation
> 
> CPUID leaf 0xD sub-leafs 0x0 and 0x1 contain cumulative sizes for the
> enabled XSave areas. Those sizes are calculated by tallying up all the
> other sub-leafs that contain per-area size information for XSave areas
> that are currently enabled in XCr0/XSS. The current check has the logic
> inverted. Fix that.
> 
> This doesn't seem to cause problems currently, but could in the future
> if OVMF made more extensive use of XSave areas. It was noticed while
> implementing SNP-related tests for KVM Unit Tests, which re-uses the
> OVMF #VC handler in some cases.
> 
> Reported-by: Pavan Kumar Paluri <papaluri@amd.com>
> Cc: Pavan Kumar Paluri <papaluri@amd.com>
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> ---
>  OvmfPkg/Library/CcExitLib/CcExitVcHandler.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> index 985e547977..cd117d5a31 100644
> --- a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> +++ b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> @@ -1678,9 +1678,7 @@ GetCpuidXSaveSize (
>    for (Idx = 0; Idx < CpuidInfo->Count; Idx++) {
> 
>      SEV_SNP_CPUID_FUNCTION  *CpuidFn = &CpuidInfo->function[Idx];
> 
> 
> 
> -    if (!((CpuidFn->EaxIn == 0xD) &&
> 
> -          ((CpuidFn->EcxIn == 0) || (CpuidFn->EcxIn == 1))))
> 
> -    {
> 
> +    if (!((CpuidFn->EaxIn == 0xD) && (CpuidFn->EcxIn > 1))) {
> 
>        continue;
> 
>      }
> 
> 
> 
> --
> 2.25.1
> 
> 
> 
> 
> 

Re: [edk2-devel] [PATCH 4/4] OvmfPkg/CcExitLib: Use documented XSave area base size for SEV-SNP

[Yao, Jiewen]

Acked-by: Jiewen Yao <jiewen.yao@intel.com>

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Roth,
> Michael via groups.io
> Sent: Thursday, December 22, 2022 12:07 AM
> To: devel@edk2.groups.io
> Cc: Tom Lendacky <thomas.lendacky@amd.com>; Ni, Ray <ray.ni@intel.com>
> Subject: [edk2-devel] [PATCH 4/4] OvmfPkg/CcExitLib: Use documented
> XSave area base size for SEV-SNP
> 
> Currently OVMF tries to rely on the base size advertised via the CPUID
> table entries corresponding to leaf 0xD, sub-leafs 0x0/0x1. This will
> generally work for KVM guests, but might not for other SEV-SNP
> hypervisor implementations. Make the handling more robust by simply
> using the base area size documented by the APM.
> 
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> ---
>  OvmfPkg/Library/CcExitLib/CcExitVcHandler.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> index cd117d5a31..f985dcff8d 100644
> --- a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> +++ b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> @@ -1647,8 +1647,6 @@ SnpEnabled (
> 
> 
>    @param[in]      XFeaturesEnabled  Bit-mask of enabled XSAVE
> features/areas as
> 
>                                      indicated by XCR0/MSR_IA32_XSS bits
> 
> -  @param[in]      XSaveBaseSize     Base/legacy XSAVE area size (e.g. when
> 
> -                                    XCR0 is 1)
> 
>    @param[in, out] XSaveSize         Pointer to storage for calculated XSAVE
> area
> 
>                                      size
> 
>    @param[in]      Compacted         Whether or not the calculation is for the
> 
> @@ -1663,7 +1661,6 @@ STATIC
>  BOOLEAN
> 
>  GetCpuidXSaveSize (
> 
>    IN     UINT64   XFeaturesEnabled,
> 
> -  IN     UINT32   XSaveBaseSize,
> 
>    IN OUT UINT32   *XSaveSize,
> 
>    IN     BOOLEAN  Compacted
> 
>    )
> 
> @@ -1672,7 +1669,10 @@ GetCpuidXSaveSize (
>    UINT64              XFeaturesFound = 0;
> 
>    UINT32              Idx;
> 
> 
> 
> -  *XSaveSize = XSaveBaseSize;
> 
> +  //
> 
> +  // The base/legacy XSave size is documented to be 0x240 in the APM.
> 
> +  //
> 
> +  *XSaveSize = 0x240;
> 
>    CpuidInfo  = (SEV_SNP_CPUID_INFO *)(UINT64)PcdGet32
> (PcdOvmfCpuidBase);
> 
> 
> 
>    for (Idx = 0; Idx < CpuidInfo->Count; Idx++) {
> 
> @@ -1888,7 +1888,6 @@ GetCpuidFw (
> 
> 
>      if (!GetCpuidXSaveSize (
> 
>             XCr0 | XssMsr.Uint64,
> 
> -           *Ebx,
> 
>             &XSaveSize,
> 
>             Compacted
> 
>             ))
> 
> --
> 2.25.1
> 
> 
> 
> 
> 

Re: [edk2-devel] [PATCH 2/4] OvmfPkg/AmdSevDxe: Update ConfidentialComputing blob struct definition

[Yao, Jiewen]

Acked-by: Jiewen Yao <jiewen.yao@intel.com>

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Roth,
> Michael via groups.io
> Sent: Thursday, December 22, 2022 12:07 AM
> To: devel@edk2.groups.io
> Cc: Tom Lendacky <thomas.lendacky@amd.com>; Ni, Ray <ray.ni@intel.com>
> Subject: [edk2-devel] [PATCH 2/4] OvmfPkg/AmdSevDxe: Update
> ConfidentialComputing blob struct definition
> 
> The Confidential Computing blob defined here is intended to match the
> definition defined by linux guest kernel. Previously, both definitions
> relied on natural alignment, but that relies on both OVMF and kernel
> being compiled as 64-bit. While there aren't currently any plans to
> enable SNP support for 32-bit compilations, the kernel definition has
> since been updated to use explicit padding/reserved fields to avoid
> this dependency. Update OVMF to match that definition.
> 
> While at it, also fix up the Reserved fields to match the numbering
> used in the kernel.
> 
> No functional changes (for currently-supported environments, at least).
> 
> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> ---
>  OvmfPkg/AmdSevDxe/AmdSevDxe.c                          | 4 +++-
>  OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h | 6 ++++--
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> index 8dfda961d7..00bb6e5d96 100644
> --- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> +++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> @@ -41,11 +41,13 @@ AllocateConfidentialComputingBlob (
> 
> 
>    CcBlob->Header                 = SIGNATURE_32 ('A', 'M', 'D', 'E');
> 
>    CcBlob->Version                = 1;
> 
> -  CcBlob->Reserved1              = 0;
> 
> +  CcBlob->Reserved               = 0;
> 
>    CcBlob->SecretsPhysicalAddress = (UINT64)(UINTN)FixedPcdGet32
> (PcdOvmfSnpSecretsBase);
> 
>    CcBlob->SecretsSize            = FixedPcdGet32 (PcdOvmfSnpSecretsSize);
> 
> +  CcBlob->Reserved1              = 0;
> 
>    CcBlob->CpuidPhysicalAddress   = (UINT64)(UINTN)FixedPcdGet32
> (PcdOvmfCpuidBase);
> 
>    CcBlob->CpuidLSize             = FixedPcdGet32 (PcdOvmfCpuidSize);
> 
> +  CcBlob->Reserved2              = 0;
> 
> 
> 
>    *CcBlobPtr = CcBlob;
> 
> 
> 
> diff --git a/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
> b/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
> index b328310fd0..83620e31b8 100644
> --- a/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
> +++ b/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
> @@ -18,14 +18,16 @@
>      { 0x85, 0x54, 0x93, 0xd7, 0x77, 0x91, 0x2d, 0x42 }, \
> 
>    }
> 
> 
> 
> -typedef struct {
> 
> +typedef PACKED struct {
> 
>    UINT32    Header;
> 
>    UINT16    Version;
> 
> -  UINT16    Reserved1;
> 
> +  UINT16    Reserved;
> 
>    UINT64    SecretsPhysicalAddress;
> 
>    UINT32    SecretsSize;
> 
> +  UINT32    Reserved1;
> 
>    UINT64    CpuidPhysicalAddress;
> 
>    UINT32    CpuidLSize;
> 
> +  UINT32    Reserved2;
> 
>  } CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION;
> 
> 
> 
>  extern EFI_GUID  gConfidentialComputingSevSnpBlobGuid;
> 
> --
> 2.25.1
> 
> 
> 
> 
> 

Re: [edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory

[Yao, Jiewen]

Are you sure you want to use EfiACPIReclaimMemory ?

Usually EfiACPIReclaimMemory is only for ACPI table, which can be reclaimed and used by OS, after copy ACPI table.

If you want to claim the memory owned by firmware (not owned by OS), you need use ACPINvs or reserved.


Although I don't fully understand SEV, this seems suspicious.

Please double confirm if this is really you want.

Thank you
Yao, Jiewen


> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Roth,
> Michael via groups.io
> Sent: Thursday, December 22, 2022 12:07 AM
> To: devel@edk2.groups.io
> Cc: Tom Lendacky <thomas.lendacky@amd.com>; Ni, Ray
> <ray.ni@intel.com>; Dov Murik <dovmurik@linux.ibm.com>
> Subject: [edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC
> blob as EfiACPIReclaimMemory
> 
> The SEV-SNP Confidential Computing blob contains metadata that should
> remain accessible for the life of the guest. Allocate it as
> EfiACPIReclaimMemory to ensure the memory isn't overwritten by the guest
> operating system later.
> 
> Reported-by: Dov Murik <dovmurik@linux.ibm.com>
> Suggested-by: Dov Murik <dovmurik@linux.ibm.com>
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> ---
>  OvmfPkg/AmdSevDxe/AmdSevDxe.c | 62 +++++++++++++++++++++++++++---
> -----
>  1 file changed, 48 insertions(+), 14 deletions(-)
> 
> diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> index 662d3c4ccb..8dfda961d7 100644
> --- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> +++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> @@ -21,15 +21,36 @@
>  #include <Guid/ConfidentialComputingSevSnpBlob.h>
> 
>  #include <Library/PcdLib.h>
> 
> 
> 
> -STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION
> mSnpBootDxeTable = {
> 
> -  SIGNATURE_32 ('A',                                    'M', 'D', 'E'),
> 
> -  1,
> 
> -  0,
> 
> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase),
> 
> -  FixedPcdGet32 (PcdOvmfSnpSecretsSize),
> 
> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase),
> 
> -  FixedPcdGet32 (PcdOvmfCpuidSize),
> 
> -};
> 
> +STATIC
> 
> +EFI_STATUS
> 
> +AllocateConfidentialComputingBlob (
> 
> +  OUT CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  **CcBlobPtr
> 
> +  )
> 
> +{
> 
> +  EFI_STATUS                                Status;
> 
> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *CcBlob;
> 
> +
> 
> +  Status = gBS->AllocatePool (
> 
> +                  EfiACPIReclaimMemory,
> 
> +                  sizeof (CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION),
> 
> +                  (VOID **)&CcBlob
> 
> +                  );
> 
> +  if (EFI_ERROR (Status)) {
> 
> +    return Status;
> 
> +  }
> 
> +
> 
> +  CcBlob->Header                 = SIGNATURE_32 ('A', 'M', 'D', 'E');
> 
> +  CcBlob->Version                = 1;
> 
> +  CcBlob->Reserved1              = 0;
> 
> +  CcBlob->SecretsPhysicalAddress = (UINT64)(UINTN)FixedPcdGet32
> (PcdOvmfSnpSecretsBase);
> 
> +  CcBlob->SecretsSize            = FixedPcdGet32 (PcdOvmfSnpSecretsSize);
> 
> +  CcBlob->CpuidPhysicalAddress   = (UINT64)(UINTN)FixedPcdGet32
> (PcdOvmfCpuidBase);
> 
> +  CcBlob->CpuidLSize             = FixedPcdGet32 (PcdOvmfCpuidSize);
> 
> +
> 
> +  *CcBlobPtr = CcBlob;
> 
> +
> 
> +  return EFI_SUCCESS;
> 
> +}
> 
> 
> 
>  EFI_STATUS
> 
>  EFIAPI
> 
> @@ -38,10 +59,11 @@ AmdSevDxeEntryPoint (
>    IN EFI_SYSTEM_TABLE  *SystemTable
> 
>    )
> 
>  {
> 
> -  EFI_STATUS                       Status;
> 
> -  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *AllDescMap;
> 
> -  UINTN                            NumEntries;
> 
> -  UINTN                            Index;
> 
> +  EFI_STATUS                                Status;
> 
> +  EFI_GCD_MEMORY_SPACE_DESCRIPTOR           *AllDescMap;
> 
> +  UINTN                                     NumEntries;
> 
> +  UINTN                                     Index;
> 
> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *SnpBootDxeTable;
> 
> 
> 
>    //
> 
>    // Do nothing when SEV is not enabled
> 
> @@ -147,6 +169,18 @@ AmdSevDxeEntryPoint (
>      }
> 
>    }
> 
> 
> 
> +  Status = AllocateConfidentialComputingBlob (&SnpBootDxeTable);
> 
> +  if (EFI_ERROR (Status)) {
> 
> +    DEBUG ((
> 
> +      DEBUG_ERROR,
> 
> +      "%a: AllocateConfidentialComputingBlob(): %r\n",
> 
> +      __FUNCTION__,
> 
> +      Status
> 
> +      ));
> 
> +    ASSERT (FALSE);
> 
> +    CpuDeadLoop ();
> 
> +  }
> 
> +
> 
>    //
> 
>    // If its SEV-SNP active guest then install the
> CONFIDENTIAL_COMPUTING_SEV_SNP_BLOB.
> 
>    // It contains the location for both the Secrets and CPUID page.
> 
> @@ -154,7 +188,7 @@ AmdSevDxeEntryPoint (
>    if (MemEncryptSevSnpIsEnabled ()) {
> 
>      return gBS->InstallConfigurationTable (
> 
>                    &gConfidentialComputingSevSnpBlobGuid,
> 
> -                  &mSnpBootDxeTable
> 
> +                  SnpBootDxeTable
> 
>                    );
> 
>    }
> 
> 
> 
> --
> 2.25.1
> 
> 
> 
> 
> 

Re: [edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory

[Dov Murik]

Hi Jiewen,

On 06/01/2023 11:18, Yao, Jiewen wrote:
> Are you sure you want to use EfiACPIReclaimMemory ?
> 
> Usually EfiACPIReclaimMemory is only for ACPI table, which can be reclaimed and used by OS, after copy ACPI table.
> 
> If you want to claim the memory owned by firmware (not owned by OS), you need use ACPINvs or reserved.
> 

EfiACPIReclaimMemory type was suggested by Ard [1] for a similar fix
another SEV-related memory area that should remain in-place throughout
the guest OS lifetime (not reused by OS).

Ard -- can you please explain that choice?


[1] https://edk2.groups.io/g/devel/message/97154



-Dov


> 
> Although I don't fully understand SEV, this seems suspicious.
> 
> Please double confirm if this is really you want.
> 
> Thank you
> Yao, Jiewen
> 
> 
>> -----Original Message-----
>> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Roth,
>> Michael via groups.io
>> Sent: Thursday, December 22, 2022 12:07 AM
>> To: devel@edk2.groups.io
>> Cc: Tom Lendacky <thomas.lendacky@amd.com>; Ni, Ray
>> <ray.ni@intel.com>; Dov Murik <dovmurik@linux.ibm.com>
>> Subject: [edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC
>> blob as EfiACPIReclaimMemory
>>
>> The SEV-SNP Confidential Computing blob contains metadata that should
>> remain accessible for the life of the guest. Allocate it as
>> EfiACPIReclaimMemory to ensure the memory isn't overwritten by the guest
>> operating system later.
>>
>> Reported-by: Dov Murik <dovmurik@linux.ibm.com>
>> Suggested-by: Dov Murik <dovmurik@linux.ibm.com>
>> Signed-off-by: Michael Roth <michael.roth@amd.com>
>> ---
>>  OvmfPkg/AmdSevDxe/AmdSevDxe.c | 62 +++++++++++++++++++++++++++---
>> -----
>>  1 file changed, 48 insertions(+), 14 deletions(-)
>>
>> diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
>> b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
>> index 662d3c4ccb..8dfda961d7 100644
>> --- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
>> +++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
>> @@ -21,15 +21,36 @@
>>  #include <Guid/ConfidentialComputingSevSnpBlob.h>
>>
>>  #include <Library/PcdLib.h>
>>
>>
>>
>> -STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION
>> mSnpBootDxeTable = {
>>
>> -  SIGNATURE_32 ('A',                                    'M', 'D', 'E'),
>>
>> -  1,
>>
>> -  0,
>>
>> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase),
>>
>> -  FixedPcdGet32 (PcdOvmfSnpSecretsSize),
>>
>> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase),
>>
>> -  FixedPcdGet32 (PcdOvmfCpuidSize),
>>
>> -};
>>
>> +STATIC
>>
>> +EFI_STATUS
>>
>> +AllocateConfidentialComputingBlob (
>>
>> +  OUT CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  **CcBlobPtr
>>
>> +  )
>>
>> +{
>>
>> +  EFI_STATUS                                Status;
>>
>> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *CcBlob;
>>
>> +
>>
>> +  Status = gBS->AllocatePool (
>>
>> +                  EfiACPIReclaimMemory,
>>
>> +                  sizeof (CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION),
>>
>> +                  (VOID **)&CcBlob
>>
>> +                  );
>>
>> +  if (EFI_ERROR (Status)) {
>>
>> +    return Status;
>>
>> +  }
>>
>> +
>>
>> +  CcBlob->Header                 = SIGNATURE_32 ('A', 'M', 'D', 'E');
>>
>> +  CcBlob->Version                = 1;
>>
>> +  CcBlob->Reserved1              = 0;
>>
>> +  CcBlob->SecretsPhysicalAddress = (UINT64)(UINTN)FixedPcdGet32
>> (PcdOvmfSnpSecretsBase);
>>
>> +  CcBlob->SecretsSize            = FixedPcdGet32 (PcdOvmfSnpSecretsSize);
>>
>> +  CcBlob->CpuidPhysicalAddress   = (UINT64)(UINTN)FixedPcdGet32
>> (PcdOvmfCpuidBase);
>>
>> +  CcBlob->CpuidLSize             = FixedPcdGet32 (PcdOvmfCpuidSize);
>>
>> +
>>
>> +  *CcBlobPtr = CcBlob;
>>
>> +
>>
>> +  return EFI_SUCCESS;
>>
>> +}
>>
>>
>>
>>  EFI_STATUS
>>
>>  EFIAPI
>>
>> @@ -38,10 +59,11 @@ AmdSevDxeEntryPoint (
>>    IN EFI_SYSTEM_TABLE  *SystemTable
>>
>>    )
>>
>>  {
>>
>> -  EFI_STATUS                       Status;
>>
>> -  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *AllDescMap;
>>
>> -  UINTN                            NumEntries;
>>
>> -  UINTN                            Index;
>>
>> +  EFI_STATUS                                Status;
>>
>> +  EFI_GCD_MEMORY_SPACE_DESCRIPTOR           *AllDescMap;
>>
>> +  UINTN                                     NumEntries;
>>
>> +  UINTN                                     Index;
>>
>> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *SnpBootDxeTable;
>>
>>
>>
>>    //
>>
>>    // Do nothing when SEV is not enabled
>>
>> @@ -147,6 +169,18 @@ AmdSevDxeEntryPoint (
>>      }
>>
>>    }
>>
>>
>>
>> +  Status = AllocateConfidentialComputingBlob (&SnpBootDxeTable);
>>
>> +  if (EFI_ERROR (Status)) {
>>
>> +    DEBUG ((
>>
>> +      DEBUG_ERROR,
>>
>> +      "%a: AllocateConfidentialComputingBlob(): %r\n",
>>
>> +      __FUNCTION__,
>>
>> +      Status
>>
>> +      ));
>>
>> +    ASSERT (FALSE);
>>
>> +    CpuDeadLoop ();
>>
>> +  }
>>
>> +
>>
>>    //
>>
>>    // If its SEV-SNP active guest then install the
>> CONFIDENTIAL_COMPUTING_SEV_SNP_BLOB.
>>
>>    // It contains the location for both the Secrets and CPUID page.
>>
>> @@ -154,7 +188,7 @@ AmdSevDxeEntryPoint (
>>    if (MemEncryptSevSnpIsEnabled ()) {
>>
>>      return gBS->InstallConfigurationTable (
>>
>>                    &gConfidentialComputingSevSnpBlobGuid,
>>
>> -                  &mSnpBootDxeTable
>>
>> +                  SnpBootDxeTable
>>
>>                    );
>>
>>    }
>>
>>
>>
>> --
>> 2.25.1
>>
>>
>>
>> 
>>
> 

Re: [edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory

[Yao, Jiewen]

Hi Dov/Ard
Please allow me to clarify:

EfiACPIReclaimMemory in UEFI spec means: OS may use the memory, after it copies the ACPI table to its own location. It is also called "AddressRangeACPI" in ACPI spec.

[2] https://uefi.org/specs/ACPI/6.5/15_System_Address_Map_Interfaces.html, search AddressRangeACPI.
[3] https://uefi.org/specs/UEFI/2.10/07_Services_Boot_Services.html, search EfiACPIReclaimMemory.

However, in the description, you mentioned "The SEV-SNP Confidential Computing blob contains metadata that should remain accessible for the life of the guest."
That requirement conflicts with the definition of ACPIReclaim memory.

I would like to suggest either of below, to meet the need "that should remain accessible for the life of the guest."
a) EfiACPIMemoryNVS in UEFI, also known as AddressRangeNVS in ACPI (or)
b) EfiReservedMemoryType in UEFI, also knowns as AddressRangeReserved in ACPI.

Please double confirm that.

Thank you
Yao, Jiewen

> -----Original Message-----
> From: Dov Murik <dovmurik@linux.ibm.com>
> Sent: Saturday, January 7, 2023 4:26 AM
> To: Yao, Jiewen <jiewen.yao@intel.com>; devel@edk2.groups.io;
> Michael.Roth@amd.com; Ard Biesheuvel <ardb@kernel.org>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>; Ni, Ray
> <ray.ni@intel.com>; Dov Murik <dovmurik@linux.ibm.com>
> Subject: Re: [edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-
> SNP CC blob as EfiACPIReclaimMemory
> 
> Hi Jiewen,
> 
> On 06/01/2023 11:18, Yao, Jiewen wrote:
> > Are you sure you want to use EfiACPIReclaimMemory ?
> >
> > Usually EfiACPIReclaimMemory is only for ACPI table, which can be
> reclaimed and used by OS, after copy ACPI table.
> >
> > If you want to claim the memory owned by firmware (not owned by OS),
> you need use ACPINvs or reserved.
> >
> 
> EfiACPIReclaimMemory type was suggested by Ard [1] for a similar fix
> another SEV-related memory area that should remain in-place throughout
> the guest OS lifetime (not reused by OS).
> 
> Ard -- can you please explain that choice?
> 
> 
> [1] https://edk2.groups.io/g/devel/message/97154
> 
> 
> 
> -Dov
> 
> 
> >
> > Although I don't fully understand SEV, this seems suspicious.
> >
> > Please double confirm if this is really you want.
> >
> > Thank you
> > Yao, Jiewen
> >
> >
> >> -----Original Message-----
> >> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Roth,
> >> Michael via groups.io
> >> Sent: Thursday, December 22, 2022 12:07 AM
> >> To: devel@edk2.groups.io
> >> Cc: Tom Lendacky <thomas.lendacky@amd.com>; Ni, Ray
> >> <ray.ni@intel.com>; Dov Murik <dovmurik@linux.ibm.com>
> >> Subject: [edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP
> CC
> >> blob as EfiACPIReclaimMemory
> >>
> >> The SEV-SNP Confidential Computing blob contains metadata that should
> >> remain accessible for the life of the guest. Allocate it as
> >> EfiACPIReclaimMemory to ensure the memory isn't overwritten by the
> guest
> >> operating system later.
> >>
> >> Reported-by: Dov Murik <dovmurik@linux.ibm.com>
> >> Suggested-by: Dov Murik <dovmurik@linux.ibm.com>
> >> Signed-off-by: Michael Roth <michael.roth@amd.com>
> >> ---
> >>  OvmfPkg/AmdSevDxe/AmdSevDxe.c | 62
> +++++++++++++++++++++++++++---
> >> -----
> >>  1 file changed, 48 insertions(+), 14 deletions(-)
> >>
> >> diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> >> b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> >> index 662d3c4ccb..8dfda961d7 100644
> >> --- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> >> +++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> >> @@ -21,15 +21,36 @@
> >>  #include <Guid/ConfidentialComputingSevSnpBlob.h>
> >>
> >>  #include <Library/PcdLib.h>
> >>
> >>
> >>
> >> -STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION
> >> mSnpBootDxeTable = {
> >>
> >> -  SIGNATURE_32 ('A',                                    'M', 'D', 'E'),
> >>
> >> -  1,
> >>
> >> -  0,
> >>
> >> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase),
> >>
> >> -  FixedPcdGet32 (PcdOvmfSnpSecretsSize),
> >>
> >> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase),
> >>
> >> -  FixedPcdGet32 (PcdOvmfCpuidSize),
> >>
> >> -};
> >>
> >> +STATIC
> >>
> >> +EFI_STATUS
> >>
> >> +AllocateConfidentialComputingBlob (
> >>
> >> +  OUT CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  **CcBlobPtr
> >>
> >> +  )
> >>
> >> +{
> >>
> >> +  EFI_STATUS                                Status;
> >>
> >> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *CcBlob;
> >>
> >> +
> >>
> >> +  Status = gBS->AllocatePool (
> >>
> >> +                  EfiACPIReclaimMemory,
> >>
> >> +                  sizeof (CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION),
> >>
> >> +                  (VOID **)&CcBlob
> >>
> >> +                  );
> >>
> >> +  if (EFI_ERROR (Status)) {
> >>
> >> +    return Status;
> >>
> >> +  }
> >>
> >> +
> >>
> >> +  CcBlob->Header                 = SIGNATURE_32 ('A', 'M', 'D', 'E');
> >>
> >> +  CcBlob->Version                = 1;
> >>
> >> +  CcBlob->Reserved1              = 0;
> >>
> >> +  CcBlob->SecretsPhysicalAddress = (UINT64)(UINTN)FixedPcdGet32
> >> (PcdOvmfSnpSecretsBase);
> >>
> >> +  CcBlob->SecretsSize            = FixedPcdGet32 (PcdOvmfSnpSecretsSize);
> >>
> >> +  CcBlob->CpuidPhysicalAddress   = (UINT64)(UINTN)FixedPcdGet32
> >> (PcdOvmfCpuidBase);
> >>
> >> +  CcBlob->CpuidLSize             = FixedPcdGet32 (PcdOvmfCpuidSize);
> >>
> >> +
> >>
> >> +  *CcBlobPtr = CcBlob;
> >>
> >> +
> >>
> >> +  return EFI_SUCCESS;
> >>
> >> +}
> >>
> >>
> >>
> >>  EFI_STATUS
> >>
> >>  EFIAPI
> >>
> >> @@ -38,10 +59,11 @@ AmdSevDxeEntryPoint (
> >>    IN EFI_SYSTEM_TABLE  *SystemTable
> >>
> >>    )
> >>
> >>  {
> >>
> >> -  EFI_STATUS                       Status;
> >>
> >> -  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *AllDescMap;
> >>
> >> -  UINTN                            NumEntries;
> >>
> >> -  UINTN                            Index;
> >>
> >> +  EFI_STATUS                                Status;
> >>
> >> +  EFI_GCD_MEMORY_SPACE_DESCRIPTOR           *AllDescMap;
> >>
> >> +  UINTN                                     NumEntries;
> >>
> >> +  UINTN                                     Index;
> >>
> >> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *SnpBootDxeTable;
> >>
> >>
> >>
> >>    //
> >>
> >>    // Do nothing when SEV is not enabled
> >>
> >> @@ -147,6 +169,18 @@ AmdSevDxeEntryPoint (
> >>      }
> >>
> >>    }
> >>
> >>
> >>
> >> +  Status = AllocateConfidentialComputingBlob (&SnpBootDxeTable);
> >>
> >> +  if (EFI_ERROR (Status)) {
> >>
> >> +    DEBUG ((
> >>
> >> +      DEBUG_ERROR,
> >>
> >> +      "%a: AllocateConfidentialComputingBlob(): %r\n",
> >>
> >> +      __FUNCTION__,
> >>
> >> +      Status
> >>
> >> +      ));
> >>
> >> +    ASSERT (FALSE);
> >>
> >> +    CpuDeadLoop ();
> >>
> >> +  }
> >>
> >> +
> >>
> >>    //
> >>
> >>    // If its SEV-SNP active guest then install the
> >> CONFIDENTIAL_COMPUTING_SEV_SNP_BLOB.
> >>
> >>    // It contains the location for both the Secrets and CPUID page.
> >>
> >> @@ -154,7 +188,7 @@ AmdSevDxeEntryPoint (
> >>    if (MemEncryptSevSnpIsEnabled ()) {
> >>
> >>      return gBS->InstallConfigurationTable (
> >>
> >>                    &gConfidentialComputingSevSnpBlobGuid,
> >>
> >> -                  &mSnpBootDxeTable
> >>
> >> +                  SnpBootDxeTable
> >>
> >>                    );
> >>
> >>    }
> >>
> >>
> >>
> >> --
> >> 2.25.1
> >>
> >>
> >>
> >> 
> >>
> >

Re: [edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory

[Ard Biesheuvel]

On Sat, 7 Jan 2023 at 03:01, Yao, Jiewen <jiewen.yao@intel.com> wrote:
>
> Hi Dov/Ard
> Please allow me to clarify:
>
> EfiACPIReclaimMemory in UEFI spec means: OS may use the memory, after it copies the ACPI table to its own location. It is also called "AddressRangeACPI" in ACPI spec.
>
> [2] https://uefi.org/specs/ACPI/6.5/15_System_Address_Map_Interfaces.html, search AddressRangeACPI.
> [3] https://uefi.org/specs/UEFI/2.10/07_Services_Boot_Services.html, search EfiACPIReclaimMemory.
>
> However, in the description, you mentioned "The SEV-SNP Confidential Computing blob contains metadata that should remain accessible for the life of the guest."
> That requirement conflicts with the definition of ACPIReclaim memory.
>
> I would like to suggest either of below, to meet the need "that should remain accessible for the life of the guest."
> a) EfiACPIMemoryNVS in UEFI, also known as AddressRangeNVS in ACPI (or)
> b) EfiReservedMemoryType in UEFI, also knowns as AddressRangeReserved in ACPI.
>
> Please double confirm that.
>

If EfiACPIMemoryNVS is considered more appropriate, I don't have any
issues with that.

But the patch is correct in the sense that it should not use
statically allocated objects. And EfiRuntimeServicesData should be
avoided as well (athough it is often used for cases like this) as it
will end up getting mapped into the firmware page tables for no
reason.

EfiReservedMemory is not suitable for this - Linux on ARM must omit
this from all its mappings of system memory, because the OS does not
know *why* it is reserved and with which attributes it is being
mapped, and the architecture does not tolerate duplicate mappings with
mismatched attributes.

The semantics of EfiAcpiReclaimMemory are also suitable for cases
where the contents of the region is only relevant to the OS, and not
to the firmware itself, and it is really up to the OS to decided
whether or not it will reclaim the region in question. So for passing
tables in memory that are similar in purpose to ACPI tables (i.e.,
describe the platform to the OS), EfiAcpiReclaimMemory is suitable
imho.

Re: [edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory

[Yao, Jiewen]

Never mind. I don’t have concern for SEV code.

You may merge it, if you think it is OK.


> -----Original Message-----
> From: Ard Biesheuvel <ardb@kernel.org>
> Sent: Sunday, January 8, 2023 12:53 AM
> To: Yao, Jiewen <jiewen.yao@intel.com>
> Cc: Dov Murik <dovmurik@linux.ibm.com>; devel@edk2.groups.io;
> Michael.Roth@amd.com; Tom Lendacky <thomas.lendacky@amd.com>; Ni,
> Ray <ray.ni@intel.com>
> Subject: Re: [edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-
> SNP CC blob as EfiACPIReclaimMemory
> 
> On Sat, 7 Jan 2023 at 03:01, Yao, Jiewen <jiewen.yao@intel.com> wrote:
> >
> > Hi Dov/Ard
> > Please allow me to clarify:
> >
> > EfiACPIReclaimMemory in UEFI spec means: OS may use the memory, after
> it copies the ACPI table to its own location. It is also called
> "AddressRangeACPI" in ACPI spec.
> >
> > [2]
> https://uefi.org/specs/ACPI/6.5/15_System_Address_Map_Interfaces.html,
> search AddressRangeACPI.
> > [3] https://uefi.org/specs/UEFI/2.10/07_Services_Boot_Services.html,
> search EfiACPIReclaimMemory.
> >
> > However, in the description, you mentioned "The SEV-SNP Confidential
> Computing blob contains metadata that should remain accessible for the life
> of the guest."
> > That requirement conflicts with the definition of ACPIReclaim memory.
> >
> > I would like to suggest either of below, to meet the need "that should
> remain accessible for the life of the guest."
> > a) EfiACPIMemoryNVS in UEFI, also known as AddressRangeNVS in ACPI (or)
> > b) EfiReservedMemoryType in UEFI, also knowns as AddressRangeReserved
> in ACPI.
> >
> > Please double confirm that.
> >
> 
> If EfiACPIMemoryNVS is considered more appropriate, I don't have any
> issues with that.
> 
> But the patch is correct in the sense that it should not use
> statically allocated objects. And EfiRuntimeServicesData should be
> avoided as well (athough it is often used for cases like this) as it
> will end up getting mapped into the firmware page tables for no
> reason.
> 
> EfiReservedMemory is not suitable for this - Linux on ARM must omit
> this from all its mappings of system memory, because the OS does not
> know *why* it is reserved and with which attributes it is being
> mapped, and the architecture does not tolerate duplicate mappings with
> mismatched attributes.
> 
> The semantics of EfiAcpiReclaimMemory are also suitable for cases
> where the contents of the region is only relevant to the OS, and not
> to the firmware itself, and it is really up to the OS to decided
> whether or not it will reclaim the region in question. So for passing
> tables in memory that are similar in purpose to ACPI tables (i.e.,
> describe the platform to the OS), EfiAcpiReclaimMemory is suitable
> imho.

Re: [PATCH 0/4] Fixes for SEV-SNP CC blob and CPUID table handling

[Yao, Jiewen]

Hi Roth
I got weird merge conflict when I try to apply the patches from email.

Would you please resubmit the patch based on latest code base?

Once I see the new version, I will try to merge them again.

Thank you
Yao, Jiewen

> -----Original Message-----
> From: Michael Roth <michael.roth@amd.com>
> Sent: Thursday, December 22, 2022 1:42 AM
> To: devel@edk2.groups.io
> Cc: Tom Lendacky <thomas.lendacky@amd.com>; Ni, Ray
> <ray.ni@intel.com>; Ard Biesheuvel <ardb+tianocore@kernel.org>; Yao,
> Jiewen <jiewen.yao@intel.com>; Gerd Hoffmann <kraxel@redhat.com>;
> Aktas, Erdem <erdemaktas@google.com>; James Bottomley
> <jejb@linux.ibm.com>; Xu, Min M <min.m.xu@intel.com>
> Subject: Re: [PATCH 0/4] Fixes for SEV-SNP CC blob and CPUID table handling
> 
> On Wed, Dec 21, 2022 at 10:06:47AM -0600, Michael Roth wrote:
> > Here are a number of fixes related to OVMF handling of the SEV-SNP
> > Confidential Computing blob and CPUID table.
> >
> > Patch #1 is a fix for recently-reported issue that can cause
> > significant problems with some SEV-SNP guest operating systems.
> > Please consider applying this patch directly if the other
> > patches in this series are held up for any reason.
> >
> > Patches 2-4 are minor changes for things that aren't currently
> > triggered in practice, but make OVMF's SEV-SNP implementation more
> > robust for different build/hypervisor environments in the future.
> > Patch #2 was submitted previously, but refreshed here to apply
> > cleanly on top of Patch #1, with no other functional changes since
> > the initial review.
> >
> > ----------------------------------------------------------------
> > Michael Roth (4):
> >       OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as
> EfiACPIReclaimMemory
> >       OvmfPkg/AmdSevDxe: Update ConfidentialComputing blob struct
> definition
> >       OvmfPkg/CcExitLib: Fix SEV-SNP XSave area size calculation
> >       OvmfPkg/CcExitLib: Use documented XSave area base size for SEV-SNP
> 
> Adding some Cc's from Maintainers.txt that I should have included
> originally:
> 
>   Ard Biesheuvel <ardb+tianocore@kernel.org>
>   Jiewen Yao <jiewen.yao@intel.com>
>   Gerd Hoffmann <kraxel@redhat.com>
>   Erdem Aktas <erdemaktas@google.com>
>   James Bottomley <jejb@linux.ibm.com>
>   Min Xu <min.m.xu@intel.com>
> 
> Thanks,
> 
> Mike
> 
> >
> >  OvmfPkg/AmdSevDxe/AmdSevDxe.c                          | 64
> ++++++++++++++++++++++++++++++++++----------
> >  OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h |  6 +++--
> >  OvmfPkg/Library/CcExitLib/CcExitVcHandler.c            | 13 ++++-----
> >  3 files changed, 59 insertions(+), 24 deletions(-)
> >
> >