comments below:
On 05/22/17 17:23, Brijesh Singh wrote:
> When SEV is enabled, use a bounce buffer to perform the DMA operation.
>
>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Brijesh Singh <brijesh.singh@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..40b43ac78ff4 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 ()) {
> + UINTN TotalSize;
> +
> + TotalSize = sizeof (*Access);
> + //
> + // Control operation does not need buffer
> + //
(1) you missed my remark that this comment should say "skip operation",
see point (2) in
<http://mid.mail-archive.com/e6f5b576-e81d-b292-eae7-04e6088d51dd@redhat.com>.
> + if (Control != FW_CFG_DMA_CTL_SKIP) {
> + TotalSize += Size;
> + }
> +
> + //
> + // Allocate SEV DMA buffer
> + //
> + NumPages = (UINT32)EFI_SIZE_TO_PAGES (TotalSize);
> + InternalQemuFwCfgSevDmaAllocateBuffer (&BounceBuffer, NumPages);
> +
> + Access = BounceBuffer;
> + DmaBuffer = (UINT8*)BounceBuffer + sizeof (*Access);
> +
> + //
> + // Decrypt data from encrypted guest buffer into DMA buffer
> + //
> + if (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 guest buffer and
> + // free the bounce buffer
> + //
> + if (BounceBuffer) {
(2) You missed my remark about the edk2 coding style, see point (6) in
<https://www.mail-archive.com/edk2-devel@lists.01.org/msg25650.html>.
> + //
> + // Encrypt the data from DMA buffer into guest buffer
> + //
> + if (Control == FW_CFG_DMA_CTL_READ) {
> + CopyMem (Buffer, DmaBuffer, Size);
> + }
> +
> + InternalQemuFwCfgSevDmaFreeBuffer (BounceBuffer, NumPages);
> + }
> }
>
>
>
If a v6 is necessary, then please fix up the above. Otherwise, the patch
is good to me as-is.
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Thanks
Laszlo
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