From: Brijesh Singh <brijesh.si...@amd.com>
When SEV is enabled, the DMA operations must be performed on a shared
(i.e unencrypted) pages. The patch adds SEV specific hooks to use the
bounce buffer when caller map/unmap host address to a DMA address and
similarly clears/set memory encryption attribute when caller allocates
or free the DMA pages.
Signed-off-by: Brijesh Singh <brijesh.si...@amd.com>
---
OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf | 3 +-
OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c | 60 +++++++++++++++++++-
2 files changed, 61 insertions(+), 2 deletions(-)
diff --git a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
index 4ddb27d578bc..fb97caa79827 100644
--- a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
+++ b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
@@ -29,6 +29,7 @@ [Sources.common]
[Packages]
MdePkg/MdePkg.dec
MdeModulePkg/MdeModulePkg.dec
+ OvmfPkg/OvmfPkg.dec
[LibraryClasses]
BaseLib
@@ -37,5 +38,5 @@ [LibraryClasses]
DxeServicesTableLib
MemoryAllocationLib
UefiBootServicesTableLib
-
+ MemEncryptSevLib
diff --git a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
index 4a6a704f9aa5..7a79c7091004 100644
--- a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
+++ b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
@@ -25,6 +25,7 @@
#include <Library/MemoryAllocationLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/BmDmaLib.h>
+#include <Library/MemEncryptSevLib.h>
#define FORCE_BELOW_4GB_TRUE TRUE
@@ -100,6 +101,15 @@ AllocateBounceBuffer (
}
//
+ // Clear C-bit on DMA pages
+ //
+ if (MemEncryptSevIsEnabled ()) {
+ Status = MemEncryptSevClearPageEncMask (MapInfo->MappedHostAddress,
MapInfo->NumberOfPages, TRUE);
+ if (Status != EFI_SUCCESS) {
+ return Status;
+ }
+ }
+ //
// If this is a read operation from the Bus Master's point of view,
// then copy the contents of the real buffer into the mapped buffer
// so the Bus Master can read the contents of the real buffer.
@@ -170,6 +180,23 @@ BmDmaMap (
PhysicalAddress = (EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress;
if (DmaAbove4GB || (PhysicalAddress + *NumberOfBytes) <= SIZE_4GB) {
+
+ //
+ // When SEV is enabled the DMA operation must be performed on shared
pages. We force to use the
+ // bounce buffer path which will take care of allocating shared Dma
buffers mapping
+ //
+ if (MemEncryptSevIsEnabled () &&
+ (Operation == DmaOperationBusMasterRead || Operation ==
DmaOperationBusMasterWrite)) {
+ return AllocateBounceBuffer (
+ FORCE_BELOW_4GB_FALSE,
+ Operation,
+ PhysicalAddress,
+ NumberOfBytes,
+ DeviceAddress,
+ Mapping
+ );
+ }
+
//
// If we CAN handle DMA above 4GB or the transfer is below 4GB,
// the DeviceAddress is simply the HostAddress
@@ -218,7 +245,8 @@ BmDmaUnmap (
IN VOID *Mapping
)
{
- MAP_INFO *MapInfo;
+ MAP_INFO *MapInfo;
+ EFI_STATUS Status;
//
// Check for invalid inputs
@@ -251,6 +279,17 @@ BmDmaUnmap (
}
//
+ // When SEV is enabled then Dma buffer allocate by bounce buffer have C-bit
cleared,
+ // restore the C-bit before we release the resources
+ //
+ if (MemEncryptSevIsEnabled ()) {
+ Status = MemEncryptSevSetPageEncMask (MapInfo->MappedHostAddress,
MapInfo->NumberOfPages, TRUE);
+ if (Status != EFI_SUCCESS) {
+ return Status;
+ }
+ }
+
+ //
// Free the mapped buffer and the MAP_INFO structure.
//
gBS->FreePages (MapInfo->MappedHostAddress, MapInfo->NumberOfPages);
@@ -322,8 +361,15 @@ BmDmaAllocateBuffer (
);
if (!EFI_ERROR (Status)) {
*HostAddress = (VOID *) (UINTN) PhysicalAddress;
+ //
+ // Clear C-bit on Dma pages
+ //
+ if (MemEncryptSevIsEnabled ()) {
+ Status = MemEncryptSevClearPageEncMask (PhysicalAddress, Pages, TRUE);
+ }
}
+
return Status;
}
@@ -346,6 +392,18 @@ BmDmaFreeBuffer (
IN UINTN Pages
)
{
+ EFI_STATUS Status;
+
+ //
+ // Restore the C-bit on DMA pages
+ //
+ if (MemEncryptSevIsEnabled ()) {
+ Status = MemEncryptSevSetPageEncMask ((UINTN) HostAddress, Pages, TRUE);
+ if (Status != EFI_SUCCESS) {
+ return Status;
+ }
+ }
+
return gBS->FreePages ((EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress, Pages);
}
--
2.7.4
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