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OvmfPkg/MemEncryptSevLib: find pages of initial SMRAM save state map

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In the next three patches, we're going to modify three modules under
OvmfPkg. When OVMF is built with -D SMM_REQUIRE and runs in an SEV guest,
each affected module will have to know the page range that covers the
initial (pre-SMBASE relocation) SMRAM save state map. Add a helper
function to MemEncryptSevLib that calculates the "base address" and
"number of pages" constants for this page range.

(In a RELEASE build -- i.e., with assertions disabled and optimization
enabled --, the helper function can be compiled to store two constants
determined at compile time.)

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
This commit is contained in:
Laszlo Ersek 2018-03-01 17:31:44 +01:00
parent cd66bd7316
commit 61a044c6c1
3 changed files with 78 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
OvmfPkg/Include/Library/MemEncryptSevLib.h
View File

@ -86,4 +86,27 @@ MemEncryptSevSetPageEncMask (
IN UINTN NumPages,
IN BOOLEAN Flush
);
/**
Locate the page range that covers the initial (pre-SMBASE-relocation) SMRAM
Save State Map.
@param[out] BaseAddress The base address of the lowest-address page that
covers the initial SMRAM Save State Map.
@param[out] NumberOfPages The number of pages in the page range that covers
the initial SMRAM Save State Map.
@retval RETURN_SUCCESS BaseAddress and NumberOfPages have been set on
output.
@retval RETURN_UNSUPPORTED SMM is unavailable.
**/
RETURN_STATUS
EFIAPI
MemEncryptSevLocateInitialSmramSaveStateMapPages (
OUT UINTN *BaseAddress,
OUT UINTN *NumberOfPages
);
#endif // _MEM_ENCRYPT_SEV_LIB_H_

4
OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
View File

@ -51,3 +51,7 @@
CpuLib
DebugLib
MemoryAllocationLib
PcdLib
[FeaturePcd]
gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire

51
OvmfPkg/Library/BaseMemEncryptSevLib/MemEncryptSevLibInternal.c
View File

@ -17,9 +17,13 @@
#include <Library/BaseLib.h>
#include <Library/DebugLib.h>
#include <Library/MemEncryptSevLib.h>
#include <Library/PcdLib.h>
#include <Register/Amd/Cpuid.h>
#include <Register/Amd/Msr.h>
#include <Register/Cpuid.h>
#include <Register/QemuSmramSaveStateMap.h>
#include <Register/SmramSaveStateMap.h>
#include <Uefi/UefiBaseType.h>
STATIC BOOLEAN mSevStatus = FALSE;
STATIC BOOLEAN mSevStatusChecked = FALSE;
@ -87,3 +91,50 @@ MemEncryptSevIsEnabled (
return mSevStatus;
}
/**
Locate the page range that covers the initial (pre-SMBASE-relocation) SMRAM
Save State Map.
@param[out] BaseAddress The base address of the lowest-address page that
covers the initial SMRAM Save State Map.
@param[out] NumberOfPages The number of pages in the page range that covers
the initial SMRAM Save State Map.
@retval RETURN_SUCCESS BaseAddress and NumberOfPages have been set on
output.
@retval RETURN_UNSUPPORTED SMM is unavailable.
**/
RETURN_STATUS
EFIAPI
MemEncryptSevLocateInitialSmramSaveStateMapPages (
OUT UINTN *BaseAddress,
OUT UINTN *NumberOfPages
)
{
UINTN MapStart;
UINTN MapEnd;
UINTN MapPagesStart; // MapStart rounded down to page boundary
UINTN MapPagesEnd; // MapEnd rounded up to page boundary
UINTN MapPagesSize; // difference between MapPagesStart and MapPagesEnd
if (!FeaturePcdGet (PcdSmmSmramRequire)) {
return RETURN_UNSUPPORTED;
}
MapStart = SMM_DEFAULT_SMBASE + SMRAM_SAVE_STATE_MAP_OFFSET;
MapEnd = MapStart + sizeof (QEMU_SMRAM_SAVE_STATE_MAP);
MapPagesStart = MapStart & ~(UINTN)EFI_PAGE_MASK;
MapPagesEnd = ALIGN_VALUE (MapEnd, EFI_PAGE_SIZE);
MapPagesSize = MapPagesEnd - MapPagesStart;
ASSERT ((MapPagesSize & EFI_PAGE_MASK) == 0);
*BaseAddress = MapPagesStart;
*NumberOfPages = MapPagesSize >> EFI_PAGE_SHIFT;
return RETURN_SUCCESS;
}