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104 lines
4.0 KiB
104 lines
4.0 KiB
From 3ae6cb5329ce5e48efc29989943e19cfccbfb38b Mon Sep 17 00:00:00 2001
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From: Tom Lendacky <thomas.lendacky@amd.com>
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Date: Mon, 18 Nov 2024 12:59:32 -0600
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Subject: [PATCH] OvmfPkg/PlatformInitLib: Retry NV vars FV check as shared
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When OVMF is built with SECURE_BOOT_ENABLE, the variable store will be
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populated and validated in PlatformValidateNvVarStore(). When an SEV
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or an SEV-ES guest is running, this may be encrypted or unencrypted
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depending on how the guest was started. If the guest was started with the
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combined code and variable contents (OVMF.fd), then the variable store
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will be encrypted. If the guest was started with the separate code and
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variables contents (OVMF_CODE.fd and OVMF_VARS.fd), then the variable
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store will be unencrypted.
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When PlatformValidateNvVarStore() is first invoked, the variable store
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area is initially mapped encrypted, which may or may not pass the variable
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validation step depending how the guest was launched. To accomodate this,
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retry the validation step on failure after remapping the variable store
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area as unencrypted.
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Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
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(cherry picked from commit d502cc7702e4d537c2bcbe5256e26cba6d4ca8c6)
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---
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OvmfPkg/Library/PlatformInitLib/Platform.c | 32 +++++++++++++++++--
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.../PlatformInitLib/PlatformInitLib.inf | 1 +
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2 files changed, 31 insertions(+), 2 deletions(-)
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diff --git a/OvmfPkg/Library/PlatformInitLib/Platform.c b/OvmfPkg/Library/PlatformInitLib/Platform.c
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index 10fc17355f..715533b1f2 100644
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--- a/OvmfPkg/Library/PlatformInitLib/Platform.c
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+++ b/OvmfPkg/Library/PlatformInitLib/Platform.c
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@@ -34,6 +34,7 @@
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#include <Guid/VariableFormat.h>
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#include <OvmfPlatforms.h>
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#include <Library/TdxLib.h>
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+#include <Library/MemEncryptSevLib.h>
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#include <Library/PlatformInitLib.h>
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@@ -774,6 +775,8 @@ PlatformValidateNvVarStore (
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EFI_FIRMWARE_VOLUME_HEADER *NvVarStoreFvHeader;
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VARIABLE_STORE_HEADER *NvVarStoreHeader;
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AUTHENTICATED_VARIABLE_HEADER *VariableHeader;
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+ BOOLEAN Retry;
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+ EFI_STATUS Status;
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static EFI_GUID FvHdrGUID = EFI_SYSTEM_NV_DATA_FV_GUID;
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static EFI_GUID VarStoreHdrGUID = EFI_AUTHENTICATED_VARIABLE_GUID;
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@@ -792,6 +795,15 @@ PlatformValidateNvVarStore (
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//
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NvVarStoreFvHeader = (EFI_FIRMWARE_VOLUME_HEADER *)NvVarStoreBase;
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+ //
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+ // SEV and SEV-ES can use separate flash devices for OVMF code and
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+ // OVMF variables. In this case, the OVMF variables will need to be
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+ // mapped unencrypted. If the initial validation fails, remap the
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+ // NV variable store as unencrypted and retry the validation.
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+ //
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+ Retry = MemEncryptSevIsEnabled ();
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+
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+RETRY:
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if ((!IsZeroBuffer (NvVarStoreFvHeader->ZeroVector, 16)) ||
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(!CompareGuid (&FvHdrGUID, &NvVarStoreFvHeader->FileSystemGuid)) ||
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(NvVarStoreFvHeader->Signature != EFI_FVH_SIGNATURE) ||
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@@ -801,8 +813,24 @@ PlatformValidateNvVarStore (
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(NvVarStoreFvHeader->FvLength != NvVarStoreSize)
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)
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{
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- DEBUG ((DEBUG_ERROR, "NvVarStore FV headers were invalid.\n"));
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- return FALSE;
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+ if (!Retry) {
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+ DEBUG ((DEBUG_ERROR, "NvVarStore FV headers were invalid.\n"));
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+ return FALSE;
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+ }
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+
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+ DEBUG ((DEBUG_INFO, "Remapping NvVarStore as shared\n"));
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+ Status = MemEncryptSevClearMmioPageEncMask (
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+ 0,
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+ (UINTN)NvVarStoreBase,
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+ EFI_SIZE_TO_PAGES (NvVarStoreSize)
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+ );
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+ if (EFI_ERROR (Status)) {
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+ DEBUG ((DEBUG_ERROR, "Failed to map NvVarStore as shared\n"));
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+ return FALSE;
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+ }
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+
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+ Retry = FALSE;
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+ goto RETRY;
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}
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//
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diff --git a/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf b/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
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index 3e63ef4423..fb179e6791 100644
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--- a/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
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+++ b/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
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@@ -48,6 +48,7 @@
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HobLib
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QemuFwCfgLib
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QemuFwCfgSimpleParserLib
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+ MemEncryptSevLib
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MemoryAllocationLib
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MtrrLib
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PcdLib
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