[PATCH v6 29/42] OvmfPkg: Create GHCB pages for use during Pei and Dxe phase

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

Allocate memory for the GHCB pages and the per-CPU variable pages during
SEV initialization for use during Pei and Dxe phases. The GHCB page(s)
must be shared pages, so clear the encryption mask from the current page
table entries. Upon successful allocation, set the GHCB PCDs (PcdGhcbBase
and PcdGhcbSize).

The per-CPU variable page needs to be unique per AP. Using the page after
the GHCB ensures that it is unique per AP. But, it also ends up being
marked shared/unencrypted when it doesn't need to be. It is possible
during PEI to mark only the GHCB pages as shared (and that is done), but
DXE is not as easy. There needs to be a way to change the pagetables
created for DXE using CreateIdentityMappingPageTables() before switching
to them.

The GHCB pages (one per vCPU) will be used by the PEI and DXE #VC
exception handlers. The #VC exception handler will fill in the necessary
fields of the GHCB and exit to the hypervisor using the VMGEXIT
instruction. The hypervisor then accesses the GHCB associated with the
vCPU in order to perform the requested function.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 OvmfPkg/OvmfPkgIa32.dsc             |  2 ++
 OvmfPkg/OvmfPkgIa32X64.dsc          |  2 ++
 OvmfPkg/OvmfPkgX64.dsc              |  2 ++
 OvmfPkg/PlatformPei/PlatformPei.inf |  2 ++
 OvmfPkg/PlatformPei/AmdSev.c        | 38 ++++++++++++++++++++++++++++-
 5 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index d6bb1f6e795c..8934c7e78610 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -581,6 +581,8 @@ [PcdsDynamicDefault]
   gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask|0x0
 
   # Set SEV-ES defaults
+  gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbBase|0
+  gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbSize|0
   gUefiCpuPkgTokenSpaceGuid.PcdSevEsIsEnabled|0
 
 !if $(SMM_REQUIRE) == TRUE
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index 78d2107846a0..0bdff7f7db44 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -592,6 +592,8 @@ [PcdsDynamicDefault]
   gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask|0x0
 
   # Set SEV-ES defaults
+  gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbBase|0
+  gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbSize|0
   gUefiCpuPkgTokenSpaceGuid.PcdSevEsIsEnabled|0
 
 !if $(SMM_REQUIRE) == TRUE
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 65dd4c612073..6e83a1e2f39d 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -591,6 +591,8 @@ [PcdsDynamicDefault]
   gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask|0x0
 
   # Set SEV-ES defaults
+  gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbBase|0
+  gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbSize|0
   gUefiCpuPkgTokenSpaceGuid.PcdSevEsIsEnabled|0
 
 !if $(SMM_REQUIRE) == TRUE
diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index a9ad3f8ab522..c0bf4c2ee8b9 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -101,6 +101,8 @@ [Pcd]
   gEfiMdeModulePkgTokenSpaceGuid.PcdPropertiesTableEnable
   gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiS3Enable
   gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask
+  gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbBase
+  gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbSize
   gEfiSecurityPkgTokenSpaceGuid.PcdOptionRomImageVerificationPolicy
   gUefiCpuPkgTokenSpaceGuid.PcdCpuLocalApicBaseAddress
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber
diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
index 4dc5340caa7a..5f0946763507 100644
--- a/OvmfPkg/PlatformPei/AmdSev.c
+++ b/OvmfPkg/PlatformPei/AmdSev.c
@@ -10,12 +10,15 @@
 // The package level header files this module uses
 //
 #include <IndustryStandard/Q35MchIch9.h>
+#include <Library/BaseMemoryLib.h>
 #include <Library/DebugLib.h>
 #include <Library/HobLib.h>
 #include <Library/MemEncryptSevLib.h>
+#include <Library/MemoryAllocationLib.h>
 #include <Library/PcdLib.h>
 #include <PiPei.h>
 #include <Register/Amd/Cpuid.h>
+#include <Register/Amd/Msr.h>
 #include <Register/Cpuid.h>
 #include <Register/Intel/SmramSaveStateMap.h>
 
@@ -32,7 +35,10 @@ AmdSevEsInitialize (
   VOID
   )
 {
-  RETURN_STATUS     PcdStatus;
+  VOID              *GhcbBase;
+  PHYSICAL_ADDRESS  GhcbBasePa;
+  UINTN             GhcbPageCount;
+  RETURN_STATUS     PcdStatus, DecryptStatus;
 
   if (!MemEncryptSevEsIsEnabled ()) {
     return;
@@ -40,6 +46,36 @@ AmdSevEsInitialize (
 
   PcdStatus = PcdSetBoolS (PcdSevEsIsEnabled, TRUE);
   ASSERT_RETURN_ERROR (PcdStatus);
+
+  //
+  // Allocate GHCB and per-CPU variable pages.
+  //
+  GhcbPageCount = mMaxCpuCount * 2;
+  GhcbBase = AllocatePages (GhcbPageCount);
+  ASSERT (GhcbBase != NULL);
+
+  GhcbBasePa = (PHYSICAL_ADDRESS)(UINTN) GhcbBase;
+
+  DecryptStatus = MemEncryptSevClearPageEncMask (
+    0,
+    GhcbBasePa,
+    GhcbPageCount,
+    TRUE
+    );
+  ASSERT_RETURN_ERROR (DecryptStatus);
+
+  ZeroMem (GhcbBase, EFI_PAGES_TO_SIZE (GhcbPageCount));
+
+  PcdStatus = PcdSet64S (PcdGhcbBase, GhcbBasePa);
+  ASSERT_RETURN_ERROR (PcdStatus);
+  PcdStatus = PcdSet64S (PcdGhcbSize, EFI_PAGES_TO_SIZE (GhcbPageCount));
+  ASSERT_RETURN_ERROR (PcdStatus);
+
+  DEBUG ((DEBUG_INFO,
+    "SEV-ES is enabled, %lu GHCB pages allocated starting at 0x%p\n",
+    (UINT64)GhcbPageCount, GhcbBase));
+
+  AsmWriteMsr64 (MSR_SEV_ES_GHCB, GhcbBasePa);
 }
 
 /**
-- 
2.17.1