As per the discussion [1], the buffer allocated using IOMMU->AllocateBuffer()
need not result in a buffer that is immediately usable for the
DMA device operation. Client is required to call Map() unconditionally
with BusMasterCommonBuffer before performing the desired DMA bus
master operation.

[1]https://lists.01.org/pipermail/edk2-devel/2017-July/012652.html

Suggested-by: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/IoMmuDxe/AmdSevIoMmu.c | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/OvmfPkg/IoMmuDxe/AmdSevIoMmu.c b/OvmfPkg/IoMmuDxe/AmdSevIoMmu.c
index 9e78058b7242..cc3c979d4484 100644
--- a/OvmfPkg/IoMmuDxe/AmdSevIoMmu.c
+++ b/OvmfPkg/IoMmuDxe/AmdSevIoMmu.c
@@ -333,12 +333,6 @@ IoMmuAllocateBuffer (
                   );
   if (!EFI_ERROR (Status)) {
     *HostAddress = (VOID *) (UINTN) PhysicalAddress;
-
-    //
-    // Clear memory encryption mask
-    //
-    Status = MemEncryptSevClearPageEncMask (0, PhysicalAddress, Pages, TRUE);
-    ASSERT_EFI_ERROR(Status);
   }
 
   DEBUG ((DEBUG_VERBOSE, "%a Address 0x%Lx Pages 0x%Lx\n", __FUNCTION__, PhysicalAddress, Pages));
@@ -365,14 +359,6 @@ IoMmuFreeBuffer (
   IN  VOID                                     *HostAddress
   )
 {
-  EFI_STATUS  Status;
-
-  //
-  // Set memory encryption mask
-  //
-  Status = MemEncryptSevSetPageEncMask (0, (EFI_PHYSICAL_ADDRESS)(UINTN)HostAddress, Pages, TRUE);
-  ASSERT_EFI_ERROR(Status);
-
   DEBUG ((DEBUG_VERBOSE, "%a Address 0x%Lx Pages 0x%Lx\n", __FUNCTION__, (UINTN)HostAddress, Pages));
   return gBS->FreePages ((EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress, Pages);
 }
-- 
2.7.4

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On 07/31/17 21:31, Brijesh Singh wrote:
> As per the discussion [1], the buffer allocated using IOMMU->AllocateBuffer()
> need not result in a buffer that is immediately usable for the
> DMA device operation. Client is required to call Map() unconditionally
> with BusMasterCommonBuffer before performing the desired DMA bus
> master operation.
> 
> [1]https://lists.01.org/pipermail/edk2-devel/2017-July/012652.html
> 
> Suggested-by: Laszlo Ersek <lersek@redhat.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  OvmfPkg/IoMmuDxe/AmdSevIoMmu.c | 14 --------------
>  1 file changed, 14 deletions(-)
> 
> diff --git a/OvmfPkg/IoMmuDxe/AmdSevIoMmu.c b/OvmfPkg/IoMmuDxe/AmdSevIoMmu.c
> index 9e78058b7242..cc3c979d4484 100644
> --- a/OvmfPkg/IoMmuDxe/AmdSevIoMmu.c
> +++ b/OvmfPkg/IoMmuDxe/AmdSevIoMmu.c
> @@ -333,12 +333,6 @@ IoMmuAllocateBuffer (
>                    );
>    if (!EFI_ERROR (Status)) {
>      *HostAddress = (VOID *) (UINTN) PhysicalAddress;
> -
> -    //
> -    // Clear memory encryption mask
> -    //
> -    Status = MemEncryptSevClearPageEncMask (0, PhysicalAddress, Pages, TRUE);
> -    ASSERT_EFI_ERROR(Status);
>    }
>  
>    DEBUG ((DEBUG_VERBOSE, "%a Address 0x%Lx Pages 0x%Lx\n", __FUNCTION__, PhysicalAddress, Pages));
> @@ -365,14 +359,6 @@ IoMmuFreeBuffer (
>    IN  VOID                                     *HostAddress
>    )
>  {
> -  EFI_STATUS  Status;
> -
> -  //
> -  // Set memory encryption mask
> -  //
> -  Status = MemEncryptSevSetPageEncMask (0, (EFI_PHYSICAL_ADDRESS)(UINTN)HostAddress, Pages, TRUE);
> -  ASSERT_EFI_ERROR(Status);
> -
>    DEBUG ((DEBUG_VERBOSE, "%a Address 0x%Lx Pages 0x%Lx\n", __FUNCTION__, (UINTN)HostAddress, Pages));
>    return gBS->FreePages ((EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress, Pages);
>  }
> 

This looks good to me, but "IommuDxe" in the subject should be spelled
"IoMmuDxe". With that change,

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo
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