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/** @file
VMGEXIT Support Library.
Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include <Base.h>
#include <Uefi.h>
#include <Library/BaseMemoryLib.h>
#include <Library/VmgExitLib.h>
#include <Register/Amd/Msr.h>
/**
Check for VMGEXIT error
Check if the hypervisor has returned an error after completion of the VMGEXIT
by examining the SwExitInfo1 field of the GHCB.
@param[in] Ghcb A pointer to the GHCB
@retval 0 VMGEXIT succeeded.
@return Exception number to be propagated, VMGEXIT processing
did not succeed.
**/
STATIC
UINT64
VmgExitErrorCheck (
IN GHCB *Ghcb
)
{
GHCB_EVENT_INJECTION Event;
GHCB_EXIT_INFO ExitInfo;
UINT64 Status;
ExitInfo.Uint64 = Ghcb->SaveArea.SwExitInfo1;
ASSERT (
(ExitInfo.Elements.Lower32Bits == 0) ||
(ExitInfo.Elements.Lower32Bits == 1)
);
Status = 0;
if (ExitInfo.Elements.Lower32Bits == 0) {
return Status;
}
if (ExitInfo.Elements.Lower32Bits == 1) {
ASSERT (Ghcb->SaveArea.SwExitInfo2 != 0);
//
// Check that the return event is valid
//
Event.Uint64 = Ghcb->SaveArea.SwExitInfo2;
if (Event.Elements.Valid &&
(Event.Elements.Type == GHCB_EVENT_INJECTION_TYPE_EXCEPTION))
{
switch (Event.Elements.Vector) {
case GP_EXCEPTION:
case UD_EXCEPTION:
//
// Use returned event as return code
//
Status = Event.Uint64;
}
}
}
if (Status == 0) {
GHCB_EVENT_INJECTION GpEvent;
GpEvent.Uint64 = 0;
GpEvent.Elements.Vector = GP_EXCEPTION;
GpEvent.Elements.Type = GHCB_EVENT_INJECTION_TYPE_EXCEPTION;
GpEvent.Elements.Valid = 1;
Status = GpEvent.Uint64;
}
return Status;
}
/**
Perform VMGEXIT.
Sets the necessary fields of the GHCB, invokes the VMGEXIT instruction and
then handles the return actions.
@param[in, out] Ghcb A pointer to the GHCB
@param[in] ExitCode VMGEXIT code to be assigned to the SwExitCode
field of the GHCB.
@param[in] ExitInfo1 VMGEXIT information to be assigned to the
SwExitInfo1 field of the GHCB.
@param[in] ExitInfo2 VMGEXIT information to be assigned to the
SwExitInfo2 field of the GHCB.
@retval 0 VMGEXIT succeeded.
@return Exception number to be propagated, VMGEXIT
processing did not succeed.
**/
UINT64
EFIAPI
VmgExit (
IN OUT GHCB *Ghcb,
IN UINT64 ExitCode,
IN UINT64 ExitInfo1,
IN UINT64 ExitInfo2
)
{
Ghcb->SaveArea.SwExitCode = ExitCode;
Ghcb->SaveArea.SwExitInfo1 = ExitInfo1;
Ghcb->SaveArea.SwExitInfo2 = ExitInfo2;
VmgSetOffsetValid (Ghcb, GhcbSwExitCode);
VmgSetOffsetValid (Ghcb, GhcbSwExitInfo1);
VmgSetOffsetValid (Ghcb, GhcbSwExitInfo2);
//
// Guest memory is used for the guest-hypervisor communication, so fence
// the invocation of the VMGEXIT instruction to ensure GHCB accesses are
// synchronized properly.
//
MemoryFence ();
AsmVmgExit ();
MemoryFence ();
return VmgExitErrorCheck (Ghcb);
}
/**
Perform pre-VMGEXIT initialization/preparation.
Performs the necessary steps in preparation for invoking VMGEXIT. Must be
called before setting any fields within the GHCB.
@param[in, out] Ghcb A pointer to the GHCB
@param[in, out] InterruptState A pointer to hold the current interrupt
state, used for restoring in VmgDone ()
**/
VOID
EFIAPI
VmgInit (
IN OUT GHCB *Ghcb,
IN OUT BOOLEAN *InterruptState
)
{
//
// Be sure that an interrupt can't cause a #VC while the GHCB is
// being used.
//
*InterruptState = GetInterruptState ();
if (*InterruptState) {
DisableInterrupts ();
}
SetMem (&Ghcb->SaveArea, sizeof (Ghcb->SaveArea), 0);
}
/**
Perform post-VMGEXIT cleanup.
Performs the necessary steps to cleanup after invoking VMGEXIT. Must be
called after obtaining needed fields within the GHCB.
@param[in, out] Ghcb A pointer to the GHCB
@param[in] InterruptState An indicator to conditionally (re)enable
interrupts
**/
VOID
EFIAPI
VmgDone (
IN OUT GHCB *Ghcb,
IN BOOLEAN InterruptState
)
{
if (InterruptState) {
EnableInterrupts ();
}
}
/**
Marks a field at the specified offset as valid in the GHCB.
The ValidBitmap area represents the areas of the GHCB that have been marked
valid. Set the bit in ValidBitmap for the input offset.
@param[in, out] Ghcb Pointer to the Guest-Hypervisor Communication Block
@param[in] Offset Qword offset in the GHCB to mark valid
**/
VOID
EFIAPI
VmgSetOffsetValid (
IN OUT GHCB *Ghcb,
IN GHCB_REGISTER Offset
)
{
UINT32 OffsetIndex;
UINT32 OffsetBit;
OffsetIndex = Offset / 8;
OffsetBit = Offset % 8;
Ghcb->SaveArea.ValidBitmap[OffsetIndex] |= (1 << OffsetBit);
}
/**
Checks if a specified offset is valid in the GHCB.
The ValidBitmap area represents the areas of the GHCB that have been marked
valid. Return whether the bit in the ValidBitmap is set for the input offset.
@param[in] Ghcb A pointer to the GHCB
@param[in] Offset Qword offset in the GHCB to mark valid
@retval TRUE Offset is marked valid in the GHCB
@retval FALSE Offset is not marked valid in the GHCB
**/
BOOLEAN
EFIAPI
VmgIsOffsetValid (
IN GHCB *Ghcb,
IN GHCB_REGISTER Offset
)
{
UINT32 OffsetIndex;
UINT32 OffsetBit;
OffsetIndex = Offset / 8;
OffsetBit = Offset % 8;
return ((Ghcb->SaveArea.ValidBitmap[OffsetIndex] & (1 << OffsetBit)) != 0);
}
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