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/** @file
AMD SEV helper function.
Copyright (c) 2021, AMD Incorporated. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include "MpLib.h"
#include <Library/VmgExitLib.h>
#include <Register/Amd/Fam17Msr.h>
#include <Register/Amd/Ghcb.h>
/**
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
)
{
SEV_ES_SAVE_AREA *SaveArea;
IA32_CR0 ApCr0;
IA32_CR0 ResetCr0;
IA32_CR4 ApCr4;
IA32_CR4 ResetCr4;
UINTN StartIp;
UINT8 SipiVector;
UINT32 RmpAdjustStatus;
UINT64 VmgExitStatus;
MSR_SEV_ES_GHCB_REGISTER Msr;
GHCB *Ghcb;
BOOLEAN InterruptState;
UINT64 ExitInfo1;
UINT64 ExitInfo2;
//
// Allocate a single page for the SEV-ES Save Area and initialize it.
//
SaveArea = AllocateReservedPages (1);
if (!SaveArea) {
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;
//
// 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
);
ASSERT (RmpAdjustStatus == 0);
ExitInfo1 = (UINT64)ApicId << 32;
ExitInfo1 |= SVM_VMGEXIT_SNP_AP_CREATE;
ExitInfo2 = (UINT64)(UINTN)SaveArea;
Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
Ghcb = Msr.Ghcb;
VmgInit (Ghcb, &InterruptState);
Ghcb->SaveArea.Rax = SaveArea->SevFeatures;
VmgSetOffsetValid (Ghcb, GhcbRax);
VmgExitStatus = VmgExit (
Ghcb,
SVM_EXIT_SNP_AP_CREATION,
ExitInfo1,
ExitInfo2
);
VmgDone (Ghcb, InterruptState);
ASSERT (VmgExitStatus == 0);
if (VmgExitStatus != 0) {
RmpAdjustStatus = SevSnpRmpAdjust (
(EFI_PHYSICAL_ADDRESS)(UINTN)SaveArea,
FALSE
);
if (RmpAdjustStatus == 0) {
FreePages (SaveArea, 1);
} else {
DEBUG ((DEBUG_INFO, "SEV-SNP: RMPADJUST failed, leaking VMSA page\n"));
}
SaveArea = NULL;
}
if (CpuData->SevEsSaveArea) {
RmpAdjustStatus = SevSnpRmpAdjust (
(EFI_PHYSICAL_ADDRESS)(UINTN)CpuData->SevEsSaveArea,
FALSE
);
if (RmpAdjustStatus == 0) {
FreePages (CpuData->SevEsSaveArea, 1);
} else {
DEBUG ((DEBUG_INFO, "SEV-SNP: RMPADJUST failed, leaking VMSA page\n"));
}
}
CpuData->SevEsSaveArea = SaveArea;
}
/**
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;
UINT32 ApicId;
ASSERT (CpuMpData->MpCpuExchangeInfo->BufferStart < 0x100000);
CpuInfoInHob = (CPU_INFO_IN_HOB *)(UINTN)CpuMpData->CpuInfoInHob;
if (ProcessorNumber < 0) {
for (Index = 0; Index < CpuMpData->CpuCount; Index++) {
if (Index != CpuMpData->BspNumber) {
CpuData = &CpuMpData->CpuData[Index];
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);
}
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