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UefiCpuPkg/CpuExceptionHandler: Add base support for the #VC exception

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BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

Add base support to handle #VC exceptions. Update the common exception
handlers to invoke the VmgExitHandleVc () function of the VmgExitLib
library when a #VC is encountered. A non-zero return code will propagate
to the targeted exception handler.

Under SEV-ES, a DR7 read or write intercept generates a #VC exception.
To avoid exception recursion, a #VC exception will not try to read and
push the actual debug registers into the EFI_SYSTEM_CONTEXT_X64 struct
and instead push zeroes. The #VC exception handler does not make use of
the debug registers from the saved context and the exception processing
exit code does not attempt to restore the debug register values.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
This commit is contained in:
Tom Lendacky
2020-08-12 15:21:36 -05:00
committed by mergify[bot]
parent 3a4a6ead32
commit 5277540e37
10 changed files with 86 additions and 2 deletions
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20
UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiDxeSmmCpuException.c
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@@ -6,8 +6,9 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include "CpuExceptionCommon.h"
#include <Library/DebugLib.h>
#include <Library/VmgExitLib.h>
#include "CpuExceptionCommon.h"
/**
Internal worker function for common exception handler.
@@ -27,6 +28,23 @@ CommonExceptionHandlerWorker (
RESERVED_VECTORS_DATA *ReservedVectors;
EFI_CPU_INTERRUPT_HANDLER *ExternalInterruptHandler;
if (ExceptionType == VC_EXCEPTION) {
EFI_STATUS Status;
//
// #VC needs to be handled immediately upon enabling exception handling
// and therefore can't use the RegisterCpuInterruptHandler() interface.
//
// Handle the #VC:
// On EFI_SUCCESS - Exception has been handled, return
// On other - ExceptionType contains (possibly new) exception
// value
//
Status = VmgExitHandleVc (&ExceptionType, SystemContext);
if (!EFI_ERROR (Status)) {
return;
}
}
ExceptionHandlerContext = (EXCEPTION_HANDLER_CONTEXT *) (UINTN) (SystemContext.SystemContextIa32);
ReservedVectors = ExceptionHandlerData->ReservedVectors;
ExternalInterruptHandler = ExceptionHandlerData->ExternalInterruptHandler;