path: root/UefiCpuPkg/Library/MpInitLib/X64/AmdSev.c

/** @file

  AMD SEV helper function.

  Copyright (c) 2021 - 2024, AMD Incorporated. All rights reserved.<BR>

  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "MpLib.h"
#include <Library/CcExitLib.h>
#include <Register/Amd/Fam17Msr.h>
#include <Register/Amd/Ghcb.h>

#define _IS_ALIGNED(x, y)  (ALIGN_POINTER((x), (y)) == (x))

/**
  Perform the requested AP Creation action.

  @param[in]  SaveArea         Pointer to VM save area (VMSA)
  @param[in]  ApicId           APIC ID of the vCPU
  @param[in]  Action           AP action to perform

  @retval  TRUE   Action completed successfully
  @retval  FALSE  Action did not complete successfully
**/
STATIC
BOOLEAN
SevSnpPerformApAction (
  IN SEV_ES_SAVE_AREA  *SaveArea,
  IN UINT32            ApicId,
  IN UINTN             Action
  )
{
  MSR_SEV_ES_GHCB_REGISTER  Msr;
  GHCB                      *Ghcb;
  BOOLEAN                   InterruptState;
  UINT64                    ExitInfo1;
  UINT64                    ExitInfo2;
  UINT32                    RmpAdjustStatus;
  UINT64                    VmgExitStatus;

  if (Action == SVM_VMGEXIT_SNP_AP_CREATE) {
    //
    // To turn the page into a recognized VMSA page, issue RMPADJUST:
    //   Target VMPL but numerically higher than current VMPL
    //   Target PermissionMask is not used
    //
    RmpAdjustStatus = SevSnpRmpAdjust (
                        (EFI_PHYSICAL_ADDRESS)(UINTN)SaveArea,
                        TRUE
                        );
    if (RmpAdjustStatus != 0) {
      DEBUG ((DEBUG_INFO, "SEV-SNP: RMPADJUST failed for VMSA creation\n"));
      ASSERT (FALSE);

      return FALSE;
    }
  }

  ExitInfo1  = (UINT64)ApicId << 32;
  ExitInfo1 |= Action;
  ExitInfo2  = (UINT64)(UINTN)SaveArea;

  Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
  Ghcb                    = Msr.Ghcb;

  CcExitVmgInit (Ghcb, &InterruptState);

  if (Action == SVM_VMGEXIT_SNP_AP_CREATE) {
    Ghcb->SaveArea.Rax = SaveArea->SevFeatures;
    CcExitVmgSetOffsetValid (Ghcb, GhcbRax);
  }

  VmgExitStatus = CcExitVmgExit (
                    Ghcb,
                    SVM_EXIT_SNP_AP_CREATION,
                    ExitInfo1,
                    ExitInfo2
                    );

  CcExitVmgDone (Ghcb, InterruptState);

  if (VmgExitStatus != 0) {
    DEBUG ((DEBUG_INFO, "SEV-SNP: AP Destroy failed\n"));
    ASSERT (FALSE);

    return FALSE;
  }

  if (Action == SVM_VMGEXIT_SNP_AP_DESTROY) {
    //
    // Make the current VMSA not runnable and accessible to be
    // reprogrammed.
    //
    RmpAdjustStatus = SevSnpRmpAdjust (
                        (EFI_PHYSICAL_ADDRESS)(UINTN)SaveArea,
                        FALSE
                        );
    if (RmpAdjustStatus != 0) {
      DEBUG ((DEBUG_INFO, "SEV-SNP: RMPADJUST failed for VMSA reset\n"));
      ASSERT (FALSE);

      return FALSE;
    }
  }

  return TRUE;
}

/**
  Create an SEV-SNP AP save area (VMSA) for use in running the vCPU.

  @param[in]  CpuMpData        Pointer to CPU MP Data
  @param[in]  CpuData          Pointer to CPU AP Data
  @param[in]  ApicId           APIC ID of the vCPU
**/
VOID
SevSnpCreateSaveArea (
  IN CPU_MP_DATA  *CpuMpData,
  IN CPU_AP_DATA  *CpuData,
  UINT32          ApicId
  )
{
  UINT8             *Pages;
  SEV_ES_SAVE_AREA  *SaveArea;
  IA32_CR0          ApCr0;
  IA32_CR0          ResetCr0;
  IA32_CR4          ApCr4;
  IA32_CR4          ResetCr4;
  UINTN             StartIp;
  UINT8             SipiVector;

  if (CpuData->SevEsSaveArea == NULL) {
    //
    // Allocate a page for the SEV-ES Save Area and initialize it. Due to AMD
    // erratum #1467 (VMSA cannot be on a 2MB boundary), allocate an extra page
    // to choose from to work around the issue.
    //
    Pages = AllocateReservedPages (2);
    if (!Pages) {
      return;
    }

    //
    // Since page allocation works by allocating downward in the address space,
    // try to always free the first (lower address) page to limit possible holes
    // in the memory map. So, if the address of the second page is 2MB aligned,
    // then use the first page and free the second page. Otherwise, free the
    // first page and use the second page.
    //
    if (_IS_ALIGNED (Pages + EFI_PAGE_SIZE, SIZE_2MB)) {
      SaveArea = (SEV_ES_SAVE_AREA *)Pages;
      FreePages (Pages + EFI_PAGE_SIZE, 1);
    } else {
      SaveArea = (SEV_ES_SAVE_AREA *)(Pages + EFI_PAGE_SIZE);
      FreePages (Pages, 1);
    }

    CpuData->SevEsSaveArea = SaveArea;
  } else {
    SaveArea = CpuData->SevEsSaveArea;

    //
    // Tell the hypervisor to not use the current VMSA
    //
    if (!SevSnpPerformApAction (SaveArea, ApicId, SVM_VMGEXIT_SNP_AP_DESTROY)) {
      return;
    }
  }

  ZeroMem (SaveArea, EFI_PAGE_SIZE);

  //
  // Propogate the CR0.NW and CR0.CD setting to the AP
  //
  ResetCr0.UintN = 0x00000010;
  ApCr0.UintN    = CpuData->VolatileRegisters.Cr0;
  if (ApCr0.Bits.NW) {
    ResetCr0.Bits.NW = 1;
  }

  if (ApCr0.Bits.CD) {
    ResetCr0.Bits.CD = 1;
  }

  //
  // Propagate the CR4.MCE setting to the AP
  //
  ResetCr4.UintN = 0;
  ApCr4.UintN    = CpuData->VolatileRegisters.Cr4;
  if (ApCr4.Bits.MCE) {
    ResetCr4.Bits.MCE = 1;
  }

  //
  // Convert the start IP into a SIPI Vector
  //
  StartIp    = CpuMpData->MpCpuExchangeInfo->BufferStart;
  SipiVector = (UINT8)(StartIp >> 12);

  //
  // Set the CS:RIP value based on the start IP
  //
  SaveArea->Cs.Base                    = SipiVector << 12;
  SaveArea->Cs.Selector                = SipiVector << 8;
  SaveArea->Cs.Limit                   = 0xFFFF;
  SaveArea->Cs.Attributes.Bits.Present = 1;
  SaveArea->Cs.Attributes.Bits.Sbit    = 1;
  SaveArea->Cs.Attributes.Bits.Type    = SEV_ES_RESET_CODE_SEGMENT_TYPE;
  SaveArea->Rip                        = StartIp & 0xFFF;

  //
  // Set the remaining values as defined in APM for INIT
  //
  SaveArea->Ds.Limit                   = 0xFFFF;
  SaveArea->Ds.Attributes.Bits.Present = 1;
  SaveArea->Ds.Attributes.Bits.Sbit    = 1;
  SaveArea->Ds.Attributes.Bits.Type    = SEV_ES_RESET_DATA_SEGMENT_TYPE;
  SaveArea->Es                         = SaveArea->Ds;
  SaveArea->Fs                         = SaveArea->Ds;
  SaveArea->Gs                         = SaveArea->Ds;
  SaveArea->Ss                         = SaveArea->Ds;

  SaveArea->Gdtr.Limit                   = 0xFFFF;
  SaveArea->Ldtr.Limit                   = 0xFFFF;
  SaveArea->Ldtr.Attributes.Bits.Present = 1;
  SaveArea->Ldtr.Attributes.Bits.Type    = SEV_ES_RESET_LDT_TYPE;
  SaveArea->Idtr.Limit                   = 0xFFFF;
  SaveArea->Tr.Limit                     = 0xFFFF;
  SaveArea->Ldtr.Attributes.Bits.Present = 1;
  SaveArea->Ldtr.Attributes.Bits.Type    = SEV_ES_RESET_TSS_TYPE;

  SaveArea->Efer   = 0x1000;
  SaveArea->Cr4    = ResetCr4.UintN;
  SaveArea->Cr0    = ResetCr0.UintN;
  SaveArea->Dr7    = 0x0400;
  SaveArea->Dr6    = 0xFFFF0FF0;
  SaveArea->Rflags = 0x0002;
  SaveArea->GPat   = 0x0007040600070406ULL;
  SaveArea->XCr0   = 0x0001;
  SaveArea->Mxcsr  = 0x1F80;
  SaveArea->X87Ftw = 0x5555;
  SaveArea->X87Fcw = 0x0040;

  //
  // Set the SEV-SNP specific fields for the save area:
  //   VMPL - always VMPL0
  //   SEV_FEATURES - equivalent to the SEV_STATUS MSR right shifted 2 bits
  //
  SaveArea->Vmpl        = 0;
  SaveArea->SevFeatures = AsmReadMsr64 (MSR_SEV_STATUS) >> 2;

  SevSnpPerformApAction (SaveArea, ApicId, SVM_VMGEXIT_SNP_AP_CREATE);
}

/**
  Create SEV-SNP APs.

  @param[in]  CpuMpData        Pointer to CPU MP Data
  @param[in]  ProcessorNumber  The handle number of specified processor
                               (-1 for all APs)
**/
VOID
SevSnpCreateAP (
  IN CPU_MP_DATA  *CpuMpData,
  IN INTN         ProcessorNumber
  )
{
  CPU_INFO_IN_HOB    *CpuInfoInHob;
  CPU_AP_DATA        *CpuData;
  UINTN              Index;
  UINTN              MaxIndex;
  UINT32             ApicId;
  EFI_HOB_GUID_TYPE  *GuidHob;
  GHCB_APIC_IDS      *GhcbApicIds;

  ASSERT (CpuMpData->MpCpuExchangeInfo->BufferStart < 0x100000);

  CpuInfoInHob = (CPU_INFO_IN_HOB *)(UINTN)CpuMpData->CpuInfoInHob;

  if (ProcessorNumber < 0) {
    if (CpuMpData->InitFlag == ApInitConfig) {
      //
      // APs have not been started, so CpuCount is not "known" yet. Use the
      // retrieved APIC IDs to start the APs and fill out the MpLib CPU
      // information properly. CanUseSevSnpCreateAP() guarantees we have a
      // HOB when InitFlag is ApInitConfig.
      //
      GuidHob     = GetFirstGuidHob (&gGhcbApicIdsGuid);
      GhcbApicIds = (GHCB_APIC_IDS *)(*(UINTN *)GET_GUID_HOB_DATA (GuidHob));
      MaxIndex    = MIN (GhcbApicIds->NumEntries, PcdGet32 (PcdCpuMaxLogicalProcessorNumber));
    } else {
      //
      // APs have been previously started.
      //
      MaxIndex = CpuMpData->CpuCount;
    }

    for (Index = 0; Index < MaxIndex; Index++) {
      if (Index != CpuMpData->BspNumber) {
        CpuData = &CpuMpData->CpuData[Index];

        if (CpuMpData->InitFlag == ApInitConfig) {
          ApicId = GhcbApicIds->ApicIds[Index];

          //
          // For the first boot, use the BSP register information.
          //
          CopyMem (
            &CpuData->VolatileRegisters,
            &CpuMpData->CpuData[0].VolatileRegisters,
            sizeof (CpuData->VolatileRegisters)
            );
        } else {
          ApicId = CpuInfoInHob[Index].ApicId;
        }

        SevSnpCreateSaveArea (CpuMpData, CpuData, ApicId);
      }
    }
  } else {
    Index   = (UINTN)ProcessorNumber;
    CpuData = &CpuMpData->CpuData[Index];
    ApicId  = CpuInfoInHob[ProcessorNumber].ApicId,
    SevSnpCreateSaveArea (CpuMpData, CpuData, ApicId);
  }
}

/**
  Issue RMPADJUST to adjust the VMSA attribute of an SEV-SNP page.

  @param[in]  PageAddress
  @param[in]  VmsaPage

  @return  RMPADJUST return value
**/
UINT32
SevSnpRmpAdjust (
  IN  EFI_PHYSICAL_ADDRESS  PageAddress,
  IN  BOOLEAN               VmsaPage
  )
{
  UINT64  Rdx;

  //
  // The RMPADJUST instruction is used to set or clear the VMSA bit for a
  // page. The VMSA change is only made when running at VMPL0 and is ignored
  // otherwise. If too low a target VMPL is specified, the instruction can
  // succeed without changing the VMSA bit when not running at VMPL0. Using a
  // target VMPL level of 1, RMPADJUST will return a FAIL_PERMISSION error if
  // not running at VMPL0, thus ensuring that the VMSA bit is set appropriately
  // when no error is returned.
  //
  Rdx = 1;
  if (VmsaPage) {
    Rdx |= RMPADJUST_VMSA_PAGE_BIT;
  }

  return AsmRmpAdjust ((UINT64)PageAddress, 0, Rdx);
}

/**
  Determine if the SEV-SNP AP Create protocol should be used.

  @param[in]  CpuMpData  Pointer to CPU MP Data

  @retval     TRUE       Use SEV-SNP AP Create protocol
  @retval     FALSE      Do not use SEV-SNP AP Create protocol
**/
BOOLEAN
CanUseSevSnpCreateAP (
  IN  CPU_MP_DATA  *CpuMpData
  )
{
  //
  // The AP Create protocol is used for an SEV-SNP guest if
  //   - The initial configuration has been performed already or
  //   - The APIC IDs GUIDed HOB is non-zero.
  //
  if (!CpuMpData->SevSnpIsEnabled) {
    return FALSE;
  }

  if ((CpuMpData->InitFlag == ApInitConfig) && (GetFirstGuidHob (&gGhcbApicIdsGuid) == NULL)) {
    return FALSE;
  }

  return TRUE;
}