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- /** @file
- AMD Sev Dxe driver. This driver is dispatched early in DXE, due to being list
- in APRIORI. It clears C-bit from MMIO and NonExistent Memory space when SEV
- is enabled.
- Copyright (c) 2017 - 2020, AMD Inc. All rights reserved.<BR>
- SPDX-License-Identifier: BSD-2-Clause-Patent
- **/
- #include <IndustryStandard/Q35MchIch9.h>
- #include <Library/BaseLib.h>
- #include <Library/BaseMemoryLib.h>
- #include <Library/DebugLib.h>
- #include <Library/DxeServicesTableLib.h>
- #include <Library/MemEncryptSevLib.h>
- #include <Library/MemoryAllocationLib.h>
- #include <Library/UefiBootServicesTableLib.h>
- #include <Guid/ConfidentialComputingSevSnpBlob.h>
- #include <Library/PcdLib.h>
- STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION mSnpBootDxeTable = {
- SIGNATURE_32 ('A', 'M', 'D', 'E'),
- 1,
- 0,
- (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase),
- FixedPcdGet32 (PcdOvmfSnpSecretsSize),
- (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase),
- FixedPcdGet32 (PcdOvmfCpuidSize),
- };
- EFI_STATUS
- EFIAPI
- AmdSevDxeEntryPoint (
- IN EFI_HANDLE ImageHandle,
- IN EFI_SYSTEM_TABLE *SystemTable
- )
- {
- EFI_STATUS Status;
- EFI_GCD_MEMORY_SPACE_DESCRIPTOR *AllDescMap;
- UINTN NumEntries;
- UINTN Index;
- //
- // Do nothing when SEV is not enabled
- //
- if (!MemEncryptSevIsEnabled ()) {
- return EFI_UNSUPPORTED;
- }
- //
- // 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
- // MMIO space added later (eg PciRootBridge). By clearing both known MMIO and
- // NonExistent memory space can gurantee that current and furture MMIO adds
- // will have C-bit cleared.
- //
- Status = gDS->GetMemorySpaceMap (&NumEntries, &AllDescMap);
- if (!EFI_ERROR (Status)) {
- for (Index = 0; Index < NumEntries; Index++) {
- CONST EFI_GCD_MEMORY_SPACE_DESCRIPTOR *Desc;
- Desc = &AllDescMap[Index];
- if ((Desc->GcdMemoryType == EfiGcdMemoryTypeMemoryMappedIo) ||
- (Desc->GcdMemoryType == EfiGcdMemoryTypeNonExistent))
- {
- Status = MemEncryptSevClearMmioPageEncMask (
- 0,
- Desc->BaseAddress,
- EFI_SIZE_TO_PAGES (Desc->Length)
- );
- ASSERT_EFI_ERROR (Status);
- }
- }
- FreePool (AllDescMap);
- }
- //
- // If PCI Express is enabled, the MMCONFIG area has been reserved, rather
- // than marked as MMIO, and so the C-bit won't be cleared by the above walk
- // through the GCD map. Check for the MMCONFIG area and clear the C-bit for
- // the range.
- //
- if (PcdGet16 (PcdOvmfHostBridgePciDevId) == INTEL_Q35_MCH_DEVICE_ID) {
- Status = MemEncryptSevClearMmioPageEncMask (
- 0,
- FixedPcdGet64 (PcdPciExpressBaseAddress),
- EFI_SIZE_TO_PAGES (SIZE_256MB)
- );
- ASSERT_EFI_ERROR (Status);
- }
- //
- // When SMM is enabled, clear the C-bit from SMM Saved State Area
- //
- // NOTES: The SavedStateArea address cleared here is before SMBASE
- // relocation. Currently, we do not clear the SavedStateArea address after
- // SMBASE is relocated due to the following reasons:
- //
- // 1) Guest BIOS never access the relocated SavedStateArea.
- //
- // 2) The C-bit works on page-aligned address, but the SavedStateArea
- // address is not a page-aligned. Theoretically, we could roundup the address
- // and clear the C-bit of aligned address but looking carefully we found
- // that some portion of the page contains code -- which will causes a bigger
- // issues for SEV guest. When SEV is enabled, all the code must be encrypted
- // otherwise hardware will cause trap.
- //
- // We restore the C-bit for this SMM Saved State Area after SMBASE relocation
- // is completed (See OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c).
- //
- if (FeaturePcdGet (PcdSmmSmramRequire)) {
- UINTN MapPagesBase;
- UINTN MapPagesCount;
- Status = MemEncryptSevLocateInitialSmramSaveStateMapPages (
- &MapPagesBase,
- &MapPagesCount
- );
- ASSERT_EFI_ERROR (Status);
- //
- // Although these pages were set aside (i.e., allocated) by PlatformPei, we
- // could be after a warm reboot from the OS. Don't leak any stale OS data
- // to the hypervisor.
- //
- ZeroMem ((VOID *)MapPagesBase, EFI_PAGES_TO_SIZE (MapPagesCount));
- Status = MemEncryptSevClearPageEncMask (
- 0, // Cr3BaseAddress -- use current CR3
- MapPagesBase, // BaseAddress
- MapPagesCount // NumPages
- );
- if (EFI_ERROR (Status)) {
- DEBUG ((
- DEBUG_ERROR,
- "%a: MemEncryptSevClearPageEncMask(): %r\n",
- __FUNCTION__,
- Status
- ));
- ASSERT (FALSE);
- CpuDeadLoop ();
- }
- }
- //
- // If its SEV-SNP active guest then install the CONFIDENTIAL_COMPUTING_SEV_SNP_BLOB.
- // It contains the location for both the Secrets and CPUID page.
- //
- if (MemEncryptSevSnpIsEnabled ()) {
- return gBS->InstallConfigurationTable (
- &gConfidentialComputingSevSnpBlobGuid,
- &mSnpBootDxeTable
- );
- }
- return EFI_SUCCESS;
- }
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