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OvmfPkg/SmmCpuFeaturesLib: SEV: encrypt+free pages of init. save state map 

Based on the following patch from Brijesh Singh <brijesh.singh@amd.com>:

  [PATCH v2 1/2] OvmfPkg/AmdSevDxe: Clear the C-bit from SMM Saved State
  http://mid.mail-archive.com/20180228161415.28723-2-brijesh.singh@amd.com
  https://lists.01.org/pipermail/edk2-devel/2018-February/022016.html

Once PiSmmCpuDxeSmm relocates SMBASE for all VCPUs, the pages of the
initial SMRAM save state map can be re-encrypted (including zeroing them
out after setting the C-bit on them), and they can be released to DXE for
general use (undoing the allocation that we did in PlatformPei's
AmdSevInitialize() function).

The decryption of the same pages (which will occur chronologically
earlier) is implemented in the next patch; hence the "re-encryption" part
of this patch is currently a no-op. The series is structured like this in
order to be bisection-friendly. If the decryption patch preceded this
patch, then an info leak would be created while standing between the
patches.

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 20:59:12 +01:00
parent 86defc2c25
commit 5ef3b66fec
2 changed files with 40 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c
View File

@ -15,8 +15,10 @@
#include <Library/BaseLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/MemEncryptSevLib.h>
#include <Library/SmmCpuFeaturesLib.h>
#include <Library/SmmServicesTableLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <PiSmm.h>
#include <Register/QemuSmramSaveStateMap.h>
@ -185,6 +187,42 @@ SmmCpuFeaturesSmmRelocationComplete (
VOID
)
{
EFI_STATUS Status;
UINTN MapPagesBase;
UINTN MapPagesCount;
if (!MemEncryptSevIsEnabled ()) {
return;
}
//
// Now that SMBASE relocation is complete, re-encrypt the original SMRAM save
// state map's container pages, and release the pages to DXE. (The pages were
// allocated in PlatformPei.)
//
Status = MemEncryptSevLocateInitialSmramSaveStateMapPages (
&MapPagesBase,
&MapPagesCount
);
ASSERT_EFI_ERROR (Status);
Status = MemEncryptSevSetPageEncMask (
0, // Cr3BaseAddress -- use current CR3
MapPagesBase, // BaseAddress
MapPagesCount, // NumPages
TRUE // Flush
);
if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_ERROR, "%a: MemEncryptSevSetPageEncMask(): %r\n",
__FUNCTION__, Status));
ASSERT (FALSE);
CpuDeadLoop ();
}
ZeroMem ((VOID *)MapPagesBase, EFI_PAGES_TO_SIZE (MapPagesCount));
Status = gBS->FreePages (MapPagesBase, MapPagesCount);
ASSERT_EFI_ERROR (Status);
}
/**

2
OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.inf
View File

@ -36,4 +36,6 @@
BaseLib
BaseMemoryLib
DebugLib
MemEncryptSevLib
SmmServicesTableLib
UefiBootServicesTableLib