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Shim Reboot workaround #3

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Shim Reboot workaround #3

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43 changes: 43 additions & 0 deletions OvmfPkg/AmdSevDxe/AmdSevDxe.c
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
#include <Library/MemoryAllocationLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Guid/ConfidentialComputingSevSnpBlob.h>
#include <Guid/GlobalVariable.h>
#include <Library/PcdLib.h>
#include <Pi/PrePiDxeCis.h>
#include <Protocol/SevMemoryAcceptance.h>
Expand All @@ -28,6 +29,10 @@
// Present, initialized, tested bits defined in MdeModulePkg/Core/Dxe/DxeMain.h
#define EFI_MEMORY_INTERNAL_MASK 0x0700000000000000ULL

static EFI_GUID ShimLockGuid = {
0x605dab50, 0xe046, 0x4300, { 0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23 }
};

STATIC
EFI_STATUS
AllocateConfidentialComputingBlob (
Expand Down Expand Up @@ -191,6 +196,32 @@ STATIC EDKII_MEMORY_ACCEPT_PROTOCOL mMemoryAcceptProtocol = {
AmdSevMemoryAccept
};

VOID
EFIAPI
PopulateVarstore (
EFI_EVENT Event,
VOID *Context
)
{
EFI_SYSTEM_TABLE *SystemTable = (EFI_SYSTEM_TABLE *)Context;
EFI_STATUS Status;

DEBUG ((DEBUG_INFO, "Populating Varstore\n"));
UINT32 data = 1;

Status = SystemTable->RuntimeServices->SetVariable (
L"FB_NO_REBOOT",
&ShimLockGuid,
EFI_VARIABLE_RUNTIME_ACCESS | EFI_VARIABLE_BOOTSERVICE_ACCESS,
sizeof (data),
&data
);
ASSERT_EFI_ERROR (Status);

Status = SystemTable->BootServices->CloseEvent (Event);
ASSERT_EFI_ERROR (Status);
}

EFI_STATUS
EFIAPI
AmdSevDxeEntryPoint (
Expand All @@ -203,6 +234,7 @@ AmdSevDxeEntryPoint (
UINTN NumEntries;
UINTN Index;
CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION *SnpBootDxeTable;
EFI_EVENT PopulateVarstoreEvent;

//
// Do nothing when SEV is not enabled
Expand All @@ -211,6 +243,17 @@ AmdSevDxeEntryPoint (
return EFI_UNSUPPORTED;
}

// Workaround for shim fallback reboot
Status = gBS->CreateEventEx (
EVT_NOTIFY_SIGNAL,
TPL_CALLBACK,
PopulateVarstore,
SystemTable,
&gEfiEndOfDxeEventGroupGuid,
&PopulateVarstoreEvent
);
ASSERT_EFI_ERROR (Status);

//
// Iterate through the GCD map and clear the C-bit from MMIO and NonExistent
// memory space. The NonExistent memory space will be used for mapping the
Expand Down
1 change: 1 addition & 0 deletions OvmfPkg/AmdSevDxe/AmdSevDxe.inf
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,7 @@
[Guids]
gConfidentialComputingSevSnpBlobGuid
gEfiEventBeforeExitBootServicesGuid
gEfiEndOfDxeEventGroupGuid ## CONSUMES ## Event

[Pcd]
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfHostBridgePciDevId