From: "Roth, Michael via groups.io" <Michael.Roth=amd.com@groups.io>
To: <devel@edk2.groups.io>
Cc: Tom Lendacky <thomas.lendacky@amd.com>,
Ard Biesheuvel <ardb@kernel.org>,
Gerd Hoffmann <kraxel@redhat.com>,
Erdem Aktas <erdemaktas@google.com>,
Jiewen Yao <jiewen.yao@intel.com>, Min Xu <min.m.xu@intel.com>,
Jianyong Wu <jianyong.wu@arm.com>,
Anatol Belski <anbelski@linux.microsoft.com>
Subject: [edk2-devel] [PATCH] OvmfPkg: Don't make APIC MMIO accesses with encryption bit set
Date: Tue, 23 Apr 2024 15:59:58 -0500 [thread overview]
Message-ID: <20240423205958.1791780-1-michael.roth@amd.com> (raw)
For the most part, OVMF will clear the encryption bit for MMIO regions,
but there is currently one known exception during SEC when the APIC
base address is accessed via MMIO with the encryption bit set for
SEV-ES/SEV-SNP guests. In the case of SEV-SNP, this requires special
handling on the hypervisor side which may not be available in the
future[1], so make the necessary changes in the SEC-configured page
table to clear the encryption bit for 4K region containing the APIC
base address.
While here, drop special handling for the APIC base address in the
SEV-ES/SNP #VC handler.
[1] https://lore.kernel.org/lkml/20240208002420.34mvemnzrwwsaesw@amd.com/#t
Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jianyong Wu <jianyong.wu@arm.com>
Cc: Anatol Belski <anbelski@linux.microsoft.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
OvmfPkg/AmdSev/AmdSevX64.fdf | 5 +-
OvmfPkg/CloudHv/CloudHvX64.fdf | 5 +-
OvmfPkg/Library/CcExitLib/CcExitVcHandler.c | 12 +---
OvmfPkg/Microvm/MicrovmX64.fdf | 3 +
OvmfPkg/OvmfPkg.dec | 5 ++
OvmfPkg/OvmfPkgX64.fdf | 5 +-
OvmfPkg/Sec/AmdSev.c | 71 +++++++++++++++++++++
OvmfPkg/Sec/AmdSev.h | 14 ++++
OvmfPkg/Sec/SecMain.c | 1 +
OvmfPkg/Sec/SecMain.inf | 2 +
10 files changed, 109 insertions(+), 14 deletions(-)
diff --git a/OvmfPkg/AmdSev/AmdSevX64.fdf b/OvmfPkg/AmdSev/AmdSevX64.fdf
index d49555c6c8..595945181c 100644
--- a/OvmfPkg/AmdSev/AmdSevX64.fdf
+++ b/OvmfPkg/AmdSev/AmdSevX64.fdf
@@ -77,7 +77,10 @@ gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase|gUefiOvmfPkgTokenSpaceGuid.Pcd
0x010C00|0x000400
gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase|gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableSize
-0x011000|0x00F000
+0x011000|0x001000
+gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableSize
+
+0x012000|0x00E000
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
0x020000|0x0E0000
diff --git a/OvmfPkg/CloudHv/CloudHvX64.fdf b/OvmfPkg/CloudHv/CloudHvX64.fdf
index eae3ada191..3e6688b103 100644
--- a/OvmfPkg/CloudHv/CloudHvX64.fdf
+++ b/OvmfPkg/CloudHv/CloudHvX64.fdf
@@ -76,7 +76,10 @@ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCp
0x00F000|0x001000
gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtr|gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtrSize
-0x010000|0x010000
+0x010000|0x001000
+gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableSize
+
+0x011000|0x00F000
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
0x020000|0x0E0000
diff --git a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
index 549375dfed..da8f1e5db9 100644
--- a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
+++ b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
@@ -98,7 +98,7 @@ UnsupportedExit (
Validate that the MMIO memory access is not to encrypted memory.
Examine the pagetable entry for the memory specified. MMIO should not be
- performed against encrypted memory. MMIO to the APIC page is always allowed.
+ performed against encrypted memory.
@param[in] Ghcb Pointer to the Guest-Hypervisor Communication Block
@param[in] MemoryAddress Memory address to validate
@@ -118,16 +118,6 @@ ValidateMmioMemory (
{
MEM_ENCRYPT_SEV_ADDRESS_RANGE_STATE State;
GHCB_EVENT_INJECTION GpEvent;
- UINTN Address;
-
- //
- // Allow APIC accesses (which will have the encryption bit set during
- // SEC and PEI phases).
- //
- Address = MemoryAddress & ~(SIZE_4KB - 1);
- if (Address == GetLocalApicBaseAddress ()) {
- return 0;
- }
State = MemEncryptSevGetAddressRangeState (
0,
diff --git a/OvmfPkg/Microvm/MicrovmX64.fdf b/OvmfPkg/Microvm/MicrovmX64.fdf
index 825bf9f5e4..055e659a35 100644
--- a/OvmfPkg/Microvm/MicrovmX64.fdf
+++ b/OvmfPkg/Microvm/MicrovmX64.fdf
@@ -62,6 +62,9 @@ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvm
0x00C000|0x001000
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupSize
+0x00D000|0x001000
+gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableSize
+
0x010000|0x010000
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 2f7bded926..b23219ebd4 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -277,6 +277,11 @@
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase|0|UINT32|0x44
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupSize|0|UINT32|0x45
+ ## Specify the extra page table needed to mark the APIC MMIO range as unencrypted.
+ # The value should be a multiple of 4KB for each.
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableBase|0x0|UINT32|0x72
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableSize|0x0|UINT32|0x73
+
## The base address and size of the SEV Launch Secret Area provisioned
# after remote attestation. If this is set in the .fdf, the platform
# is responsible for protecting the area from DXE phase overwrites.
diff --git a/OvmfPkg/OvmfPkgX64.fdf b/OvmfPkg/OvmfPkgX64.fdf
index c2d3cc901e..b6e8f43566 100644
--- a/OvmfPkg/OvmfPkgX64.fdf
+++ b/OvmfPkg/OvmfPkgX64.fdf
@@ -97,7 +97,10 @@ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCp
0x00F000|0x001000
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecSvsmCaaSize
-0x010000|0x010000
+0x010000|0x001000
+gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableSize
+
+0x011000|0x00F000
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
0x020000|0x0E0000
diff --git a/OvmfPkg/Sec/AmdSev.c b/OvmfPkg/Sec/AmdSev.c
index 520b125132..cff2ecbb8c 100644
--- a/OvmfPkg/Sec/AmdSev.c
+++ b/OvmfPkg/Sec/AmdSev.c
@@ -8,11 +8,15 @@
**/
#include <Library/BaseLib.h>
+#include <Library/CpuLib.h>
#include <Library/DebugLib.h>
+#include <Library/LocalApicLib.h>
#include <Library/MemEncryptSevLib.h>
#include <Library/BaseMemoryLib.h>
#include <Register/Amd/Ghcb.h>
#include <Register/Amd/Msr.h>
+#include <IndustryStandard/PageTable.h>
+#include <WorkArea.h>
#include "AmdSev.h"
@@ -301,3 +305,70 @@ SecValidateSystemRam (
MemEncryptSevSnpPreValidateSystemRam (Start, EFI_SIZE_TO_PAGES ((UINTN)(End - Start)));
}
}
+
+/**
+ Map known MMIO regions unencrypted if SEV-ES is active.
+
+ During early booting, page table entries default to having the encryption bit
+ set for SEV-ES/SEV-SNP guests. In cases where there is MMIO to an address, the
+ encryption bit should be cleared. Clear it here for any known MMIO accesses
+ during SEC, which is currently just the APIC base address.
+
+**/
+VOID
+SecMapApicBaseUnencrypted (
+ VOID
+ )
+{
+ PAGE_MAP_AND_DIRECTORY_POINTER *Level4Entry;
+ PAGE_MAP_AND_DIRECTORY_POINTER *Level3Entry;
+ PAGE_MAP_AND_DIRECTORY_POINTER *Level2Entry;
+ PAGE_TABLE_4K_ENTRY *Level1Entry;
+ SEC_SEV_ES_WORK_AREA *SevEsWorkArea;
+ PHYSICAL_ADDRESS Cr3;
+ UINT64 ApicAddress;
+ UINT64 PgTableMask;
+ UINT32 Level1Page;
+ UINT64 Level1Address;
+ UINT64 Level1Flags;
+ UINTN PteIndex;
+
+ if (!SevEsIsEnabled ()) {
+ return;
+ }
+
+ SevEsWorkArea = (SEC_SEV_ES_WORK_AREA *)FixedPcdGet32 (PcdSevEsWorkAreaBase);
+ ApicAddress = (UINT64)GetLocalApicBaseAddress ();
+ Level1Page = FixedPcdGet32 (PcdOvmfSecApicPageTableBase);
+ PgTableMask = PAGING_4K_ADDRESS_MASK_64;
+ PgTableMask &= ~SevEsWorkArea->EncryptionMask;
+
+ Cr3 = AsmReadCr3 ();
+ Level4Entry = (VOID *)(UINTN)(Cr3 & PgTableMask);
+ Level4Entry += (UINTN)BitFieldRead64 (ApicAddress, 39, 47);
+
+ Level3Entry = (VOID *)(UINTN)(Level4Entry->Uint64 & PgTableMask);
+ Level3Entry += (UINTN)BitFieldRead64 (ApicAddress, 30, 38);
+
+ Level2Entry = (VOID *)(UINTN)(Level3Entry->Uint64 & PgTableMask);
+ Level2Entry += (UINTN)BitFieldRead64 (ApicAddress, 21, 29);
+
+ //
+ // Get memory address including encryption bit
+ //
+ Level1Address = Level2Entry->Uint64 & PgTableMask;
+ Level1Entry = (VOID *)(UINTN)Level1Page;
+ Level1Flags = BitFieldRead64 (Level2Entry->Uint64, 0, 11);
+ Level1Flags &= IA32_PG_P | IA32_PG_RW;
+ for (PteIndex = 0; PteIndex < 512; PteIndex++, Level1Entry++, Level1Address += SIZE_4KB) {
+ Level1Entry->Uint64 = Level1Address | Level1Flags;
+
+ if (Level1Address != ApicAddress) {
+ Level1Entry->Uint64 |= SevEsWorkArea->EncryptionMask;
+ }
+ }
+
+ Level2Entry->Uint64 = (UINT64)(UINTN)Level1Page | IA32_PG_P | IA32_PG_RW;
+
+ CpuFlushTlb ();
+}
diff --git a/OvmfPkg/Sec/AmdSev.h b/OvmfPkg/Sec/AmdSev.h
index f75877096e..c5ab0d5a0b 100644
--- a/OvmfPkg/Sec/AmdSev.h
+++ b/OvmfPkg/Sec/AmdSev.h
@@ -91,4 +91,18 @@ SevSnpIsEnabled (
VOID
);
+/**
+ Map MMIO regions unencrypted if SEV-ES is active.
+
+ During early booting, page table entries default to having the encryption bit
+ set for SEV-ES/SEV-SNP guests. In cases where there is MMIO to an address, the
+ encryption bit should be cleared. Clear it here for any known MMIO accesses
+ during SEC, which is currently just the APIC base address.
+
+**/
+VOID
+SecMapApicBaseUnencrypted (
+ VOID
+ );
+
#endif
diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index a30d4ce09e..60dfa61842 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -938,6 +938,7 @@ SecCoreStartupWithStack (
// interrupts before initializing the Debug Agent and the debug timer is
// enabled.
//
+ SecMapApicBaseUnencrypted ();
InitializeApicTimer (0, MAX_UINT32, TRUE, 5);
DisableApicTimerInterrupt ();
diff --git a/OvmfPkg/Sec/SecMain.inf b/OvmfPkg/Sec/SecMain.inf
index dca932a474..7b93b4e7d0 100644
--- a/OvmfPkg/Sec/SecMain.inf
+++ b/OvmfPkg/Sec/SecMain.inf
@@ -83,6 +83,8 @@
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase
gUefiOvmfPkgTokenSpaceGuid.PcdTdxAcceptPageSize
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableBase
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableSize
[FeaturePcd]
gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire
--
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next reply other threads:[~2024-04-23 21:01 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-23 20:59 Roth, Michael via groups.io [this message]
2024-04-24 11:54 ` [edk2-devel] [PATCH] OvmfPkg: Don't make APIC MMIO accesses with encryption bit set Gerd Hoffmann
2024-04-24 14:05 ` Lendacky, Thomas via groups.io
2024-04-24 14:45 ` Gerd Hoffmann
2024-04-24 16:38 ` Lendacky, Thomas via groups.io
2024-04-24 14:50 ` Roth, Michael via groups.io
2024-04-24 16:09 ` Gerd Hoffmann
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