[edk2-devel] [PATCH v5 28/42] OvmfPkg/PlatformPei: Reserve GHCB-related areas if S3 is supported
Lendacky, Thomas
thomas.lendacky at amd.com
Mon Mar 2 23:06:59 UTC 2020
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
Protect the memory used by an SEV-ES guest when S3 is supported. This
includes the page table used to break down the 2MB page that contains
the GHCB so that it can be marked un-encrypted, as well as the GHCB
area.
Regarding the lifecycle of the GHCB-related memory areas:
PcdOvmfSecGhcbPageTableBase
PcdOvmfSecGhcbBase
(a) when and how it is initialized after first boot of the VM
If SEV-ES is enabled, the GHCB-related areas are initialized during
the SEC phase [OvmfPkg/ResetVector/Ia32/PageTables64.asm].
(b) how it is protected from memory allocations during DXE
If S3 and SEV-ES are enabled, then InitializeRamRegions()
[OvmfPkg/PlatformPei/MemDetect.c] protects the ranges with an AcpiNVS
memory allocation HOB, in PEI.
If S3 is disabled, then these ranges are not protected. DXE's own page
tables are first built while still in PEI (see HandOffToDxeCore()
[MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c]). Those tables are
located in permanent PEI memory. After CR3 is switched over to them
(which occurs before jumping to the DXE core entry point), we don't have
to preserve PcdOvmfSecGhcbPageTableBase. PEI switches to GHCB pages in
permanent PEI memory and DXE will use these PEI GHCB pages, so we don't
have to preserve PcdOvmfSecGhcbBase.
(c) how it is protected from the OS
If S3 is enabled, then (b) reserves it from the OS too.
If S3 is disabled, then the range needs no protection.
(d) how it is accessed on the S3 resume path
It is rewritten same as in (a), which is fine because (b) reserved it.
(e) how it is accessed on the warm reset path
It is rewritten same as in (a).
Cc: Jordan Justen <jordan.l.justen at intel.com>
Cc: Laszlo Ersek <lersek at redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
Cc: Anthony Perard <anthony.perard at citrix.com>
Cc: Julien Grall <julien.grall at arm.com>
Reviewed-by: Laszlo Ersek <lersek at redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky at amd.com>
---
OvmfPkg/PlatformPei/PlatformPei.inf | 4 ++++
OvmfPkg/PlatformPei/MemDetect.c | 23 +++++++++++++++++++++++
2 files changed, 27 insertions(+)
diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 5b2585a4f09c..f1c2024526c8 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -72,6 +72,10 @@ [Pcd]
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesBase
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesSize
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableBase
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableSize
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBase
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbSize
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfLockBoxStorageBase
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfLockBoxStorageSize
gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize
diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index 47dc9c543719..200021098161 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -27,6 +27,7 @@ Module Name:
#include <Library/DebugLib.h>
#include <Library/HobLib.h>
#include <Library/IoLib.h>
+#include <Library/MemEncryptSevLib.h>
#include <Library/PcdLib.h>
#include <Library/PciLib.h>
#include <Library/PeimEntryPoint.h>
@@ -860,6 +861,28 @@ InitializeRamRegions (
(UINT64)(UINTN) PcdGet32 (PcdOvmfSecPageTablesSize),
EfiACPIMemoryNVS
);
+
+ if (MemEncryptSevEsIsEnabled ()) {
+ //
+ // If SEV-ES is enabled, reserve the GHCB-related memory area. This
+ // includes the extra page table used to break down the 2MB page
+ // mapping into 4KB page entries where the GHCB resides and the
+ // GHCB area itself.
+ //
+ // Since this memory range will be used by the Reset Vector on S3
+ // resume, it must be reserved as ACPI NVS.
+ //
+ BuildMemoryAllocationHob (
+ (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdOvmfSecGhcbPageTableBase),
+ (UINT64)(UINTN) PcdGet32 (PcdOvmfSecGhcbPageTableSize),
+ EfiACPIMemoryNVS
+ );
+ BuildMemoryAllocationHob (
+ (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdOvmfSecGhcbBase),
+ (UINT64)(UINTN) PcdGet32 (PcdOvmfSecGhcbSize),
+ EfiACPIMemoryNVS
+ );
+ }
#endif
}
--
2.17.1
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