/** @file
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X64 #VC Exception Handler functon.
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Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
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SPDX-License-Identifier: BSD-2-Clause-Patent
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**/
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#include <Base.h>
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#include <Uefi.h>
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#include <Library/BaseMemoryLib.h>
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#include <Library/MemEncryptSevLib.h>
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#include <Library/VmgExitLib.h>
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#include <Register/Amd/Msr.h>
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#include "VmgExitVcHandler.h"
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/**
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Handle a #VC exception.
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Performs the necessary processing to handle a #VC exception.
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@param[in, out] ExceptionType Pointer to an EFI_EXCEPTION_TYPE to be set
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as value to use on error.
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@param[in, out] SystemContext Pointer to EFI_SYSTEM_CONTEXT
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@retval EFI_SUCCESS Exception handled
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@retval EFI_UNSUPPORTED #VC not supported, (new) exception value to
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propagate provided
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@retval EFI_PROTOCOL_ERROR #VC handling failed, (new) exception value to
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propagate provided
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**/
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EFI_STATUS
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EFIAPI
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VmgExitHandleVc (
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IN OUT EFI_EXCEPTION_TYPE *ExceptionType,
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IN OUT EFI_SYSTEM_CONTEXT SystemContext
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)
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{
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MSR_SEV_ES_GHCB_REGISTER Msr;
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GHCB *Ghcb;
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GHCB *GhcbBackup;
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EFI_STATUS VcRet;
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BOOLEAN InterruptState;
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SEV_ES_PER_CPU_DATA *SevEsData;
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InterruptState = GetInterruptState ();
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if (InterruptState) {
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DisableInterrupts ();
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}
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Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
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ASSERT (Msr.GhcbInfo.Function == 0);
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ASSERT (Msr.Ghcb != 0);
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Ghcb = Msr.Ghcb;
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GhcbBackup = NULL;
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SevEsData = (SEV_ES_PER_CPU_DATA *) (Ghcb + 1);
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SevEsData->VcCount++;
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//
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// Check for maximum SEC #VC nesting.
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//
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if (SevEsData->VcCount > VMGEXIT_MAXIMUM_VC_COUNT) {
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VmgExitIssueAssert (SevEsData);
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} else if (SevEsData->VcCount > 1) {
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UINTN GhcbBackupSize;
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//
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// Be sure that the proper amount of pages are allocated
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//
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GhcbBackupSize = (VMGEXIT_MAXIMUM_VC_COUNT - 1) * sizeof (*Ghcb);
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if (GhcbBackupSize > FixedPcdGet32 (PcdOvmfSecGhcbBackupSize)) {
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//
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// Not enough SEC backup pages allocated.
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//
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VmgExitIssueAssert (SevEsData);
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}
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//
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// Save the active GHCB to a backup page.
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// To access the correct backup page, increment the backup page pointer
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// based on the current VcCount.
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//
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GhcbBackup = (GHCB *) FixedPcdGet32 (PcdOvmfSecGhcbBackupBase);
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GhcbBackup += (SevEsData->VcCount - 2);
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CopyMem (GhcbBackup, Ghcb, sizeof (*Ghcb));
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}
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VcRet = InternalVmgExitHandleVc (Ghcb, ExceptionType, SystemContext);
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if (GhcbBackup != NULL) {
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//
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// Restore the active GHCB from the backup page.
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//
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CopyMem (Ghcb, GhcbBackup, sizeof (*Ghcb));
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}
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SevEsData->VcCount--;
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if (InterruptState) {
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EnableInterrupts ();
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}
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return VcRet;
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}
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