OvmfPkg/Library/BaseMemEncryptSevLib/MemEncryptSevLibInternal.c

/** @file

  Secure Encrypted Virtualization (SEV) library helper function

  Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>

  This program and the accompanying materials are licensed and made available
  under the terms and conditions of the BSD License which accompanies this
  distribution.  The full text of the license may be found at
  http://opensource.org/licenses/bsd-license.php

  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/

#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;

/**

  Returns a boolean to indicate whether SEV is enabled

  @retval TRUE           SEV is enabled
  @retval FALSE          SEV is not enabled
  **/
STATIC
BOOLEAN
EFIAPI
InternalMemEncryptSevIsEnabled (
  VOID
  )
{
  UINT32                            RegEax;
  MSR_SEV_STATUS_REGISTER           Msr;
  CPUID_MEMORY_ENCRYPTION_INFO_EAX  Eax;

  //
  // Check if memory encryption leaf exist
  //
  AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
  if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) {
    //
    // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported)
    //
    AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL, NULL);

    if (Eax.Bits.SevBit) {
      //
      // Check MSR_0xC0010131 Bit 0 (Sev Enabled)
      //
      Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS);
      if (Msr.Bits.SevBit) {
        return TRUE;
      }
    }
  }

  return FALSE;
}

/**
  Returns a boolean to indicate whether SEV is enabled

  @retval TRUE           SEV is enabled
  @retval FALSE          SEV is not enabled
**/
BOOLEAN
EFIAPI
MemEncryptSevIsEnabled (
  VOID
  )
{
  if (mSevStatusChecked) {
    return mSevStatus;
  }

  mSevStatus = InternalMemEncryptSevIsEnabled();
  mSevStatusChecked = TRUE;

  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;
}