When SEV is enabled, the DMA must be performed on unencrypted pages.
So when get asked to perfom FWCFG DMA read or write, we allocate a
intermediate (bounce buffer) unencrypted buffer and use this buffer
for DMA read or write.
Cc: Jordan Justen <jordan.l.jus...@intel.com>
Cc: Laszlo Ersek <ler...@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Brijesh Singh <brijesh.si...@amd.com>
---
OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf | 4 +
OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c | 107 ++++++++++++++++++++
2 files changed, 111 insertions(+)
diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
index 346bb881ffc1..f8df77f788b7 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
@@ -39,6 +39,7 @@ [Sources]
[Packages]
MdePkg/MdePkg.dec
+ MdeModulePkg/MdeModulePkg.dec
OvmfPkg/OvmfPkg.dec
[LibraryClasses]
@@ -47,4 +48,7 @@ [LibraryClasses]
DebugLib
IoLib
MemoryAllocationLib
+ MemEncryptSevLib
+[Protocols]
+ gEdkiiIoMmuProtocolGuid ## SOMETIMES_CONSUMES
diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
index ac05f4c347f3..059666ffa99b 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
@@ -4,6 +4,7 @@
Copyright (C) 2013, Red Hat, Inc.
Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
+ Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
This program and the accompanying materials are licensed and made available
under the terms and conditions of the BSD License which accompanies this
@@ -14,14 +15,36 @@
WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
**/
+#include "Uefi.h"
+
+#include <Protocol/IoMmu.h>
+
+#include <Library/BaseLib.h>
#include <Library/DebugLib.h>
#include <Library/QemuFwCfgLib.h>
+#include <Library/UefiBootServicesTableLib.h>
+#include <Library/MemEncryptSevLib.h>
#include "QemuFwCfgLibInternal.h"
STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
STATIC BOOLEAN mQemuFwCfgDmaSupported;
+STATIC EDKII_IOMMU_PROTOCOL *mIoMmuProtocol;
+/**
+
+ Returns a boolean indicating whether SEV is enabled
+
+ @retval TRUE SEV is enabled
+ @retval FALSE SEV is disabled
+**/
+BOOLEAN
+InternalQemuFwCfgSevIsEnabled (
+ VOID
+ )
+{
+ return MemEncryptSevIsEnabled ();
+}
/**
Returns a boolean indicating if the firmware configuration interface
@@ -79,6 +102,21 @@ QemuFwCfgInitialize (
mQemuFwCfgDmaSupported = TRUE;
DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
}
+
+ //
+ // When SEV is enabled, the AmdSevDxe driver should have installed the IoMMU
+ // protocol which must be used for mapping host buffer to DMA buffer
+ //
+ if (mQemuFwCfgDmaSupported && MemEncryptSevIsEnabled ()) {
+ EFI_STATUS Status;
+
+ Status = gBS->LocateProtocol (&gEdkiiIoMmuProtocolGuid, NULL, (VOID
**)&mIoMmuProtocol);
+ if (EFI_ERROR(Status)) {
+ DEBUG ((DEBUG_WARN, "QemuwCfgSevDma: failed to locate IoMmu protocol,
disabling DMA support\n"));
+ mQemuFwCfgDmaSupported = FALSE;
+ }
+ }
+
return RETURN_SUCCESS;
}
@@ -114,3 +152,72 @@ InternalQemuFwCfgDmaIsAvailable (
{
return mQemuFwCfgDmaSupported;
}
+
+/**
+ Allocate a bounce buffer for SEV DMA.
+
+ @param[in] NumPage Number of pages.
+ @param[out] Buffer Allocated DMA Buffer pointer
+
+**/
+VOID
+InternalQemuFwCfgSevDmaAllocateBuffer (
+ IN UINT32 NumPages,
+ OUT VOID **Buffer
+ )
+{
+ EFI_STATUS Status;
+
+ if (!mIoMmuProtocol) {
+ //
+ // We should never reach here
+ //
+ ASSERT (FALSE);
+ CpuDeadLoop ();
+ }
+
+ Status = mIoMmuProtocol->AllocateBuffer (
+ mIoMmuProtocol,
+ 0,
+ EfiBootServicesData,
+ NumPages,
+ Buffer,
+ EDKII_IOMMU_ATTRIBUTE_MEMORY_CACHED
+ );
+ ASSERT_EFI_ERROR (Status);
+
+ DEBUG ((DEBUG_VERBOSE, "QemuFwCfgSevDma allocate buffer 0x%Lx Pages %d\n",
(UINTN)Buffer, NumPages));
+
+}
+
+/**
+ Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocateBuffer
+
+ @param[in] NumPage Number of pages.
+ @param[in] Buffer DMA Buffer pointer
+
+**/
+VOID
+InternalQemuFwCfgSevDmaFreeBuffer (
+ IN VOID *Buffer,
+ IN UINT32 NumPages
+ )
+{
+ EFI_STATUS Status;
+
+ if (!mIoMmuProtocol) {
+ //
+ // We should never reach here
+ //
+ ASSERT (FALSE);
+ CpuDeadLoop ();
+ }
+
+ Status = mIoMmuProtocol->FreeBuffer (
+ mIoMmuProtocol,
+ NumPages,
+ Buffer
+ );
+ ASSERT_EFI_ERROR (Status);
+ DEBUG ((DEBUG_VERBOSE, "QemuFwCfgSevDma free buffer 0x%Lx Pages %d\n",
(UINTN)Buffer, NumPages));
+}
--
2.7.4
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