When SEV is enabled, use a bounce buffer to perform the DMA operation.
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/QemuFwCfgLib.c | 54 +++++++++++++++++++-
1 file changed, 52 insertions(+), 2 deletions(-)
diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
index 73a19772bee1..86d8bf880e71 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
@@ -72,6 +72,8 @@ InternalQemuFwCfgDmaBytes (
volatile FW_CFG_DMA_ACCESS *Access;
UINT32 AccessHigh, AccessLow;
UINT32 Status;
+ UINT32 NumPages;
+ VOID *DmaBuffer, *BounceBuffer;
ASSERT (Control == FW_CFG_DMA_CTL_WRITE || Control == FW_CFG_DMA_CTL_READ ||
Control == FW_CFG_DMA_CTL_SKIP);
@@ -80,11 +82,44 @@ InternalQemuFwCfgDmaBytes (
return;
}
- Access = &LocalAccess;
+ //
+ // When SEV is enabled then allocate DMA bounce buffer
+ //
+ if (InternalQemuFwCfgSevIsEnabled ()) {
+ UINT32 TotalSize;
+
+ TotalSize = sizeof (*Access);
+ //
+ // Control operation does not need buffer
+ //
+ if (Control != FW_CFG_DMA_CTL_SKIP) {
+ TotalSize += Size;
+ }
+
+ //
+ // Allocate SEV DMA bounce buffer
+ //
+ NumPages = EFI_SIZE_TO_PAGES (TotalSize);
+ InternalQemuFwCfgSevDmaAllocateBuffer (NumPages, &BounceBuffer);
+
+ Access = BounceBuffer;
+ DmaBuffer = BounceBuffer + sizeof (*Access);
+
+ //
+ // Copy data from Host buffer into DMA buffer
+ //
+ if (Buffer && Control == FW_CFG_DMA_CTL_WRITE) {
+ CopyMem (DmaBuffer, Buffer, Size);
+ }
+ } else {
+ Access = &LocalAccess;
+ DmaBuffer = Buffer;
+ BounceBuffer = NULL;
+ }
Access->Control = SwapBytes32 (Control);
Access->Length = SwapBytes32 (Size);
- Access->Address = SwapBytes64 ((UINTN)Buffer);
+ Access->Address = SwapBytes64 ((UINTN)DmaBuffer);
//
// Delimit the transfer from (a) modifications to Access, (b) in case of a
@@ -117,6 +152,21 @@ InternalQemuFwCfgDmaBytes (
// After a read, the caller will want to use Buffer.
//
MemoryFence ();
+
+ //
+ // If Bounce buffer was allocated then copy the data into host buffer and
+ // free the bounce buffer
+ //
+ if (BounceBuffer) {
+ //
+ // Copy data from DMA buffer into host buffer
+ //
+ if (Buffer && Control == FW_CFG_DMA_CTL_READ) {
+ CopyMem (Buffer, DmaBuffer, Size);
+ }
+
+ InternalQemuFwCfgSevDmaFreeBuffer (BounceBuffer, NumPages);
+ }
}
--
2.7.4
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