Re: [PATCH v3 7/8] OvmfPkg/VirtioNetDxe: map caller-supplied Tx packet to device-address

[Laszlo Ersek <lersek@redhat.com>]

On 09/14/17 13:08, Brijesh Singh wrote:
> When device is behind the IOMMU, driver is require to pass the device
> address of caller-supplied transmit buffer for the bus master operations.
> 
> The patch uses VirtioNetMapTxBuf() to map caller-supplied Tx packet to a
> device-address and enqueue the device address in VRING for transfer and
> perform the reverse mapping when transfer is completed so that we can
> return the caller-supplied buffer.
> 
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  OvmfPkg/VirtioNetDxe/SnpGetStatus.c | 41 +++++++++++++++-----
>  OvmfPkg/VirtioNetDxe/SnpTransmit.c  | 27 ++++++++++---
>  2 files changed, 53 insertions(+), 15 deletions(-)
> 
> diff --git a/OvmfPkg/VirtioNetDxe/SnpGetStatus.c b/OvmfPkg/VirtioNetDxe/SnpGetStatus.c
> index 694940ea1d97..f817b98801fa 100644
> --- a/OvmfPkg/VirtioNetDxe/SnpGetStatus.c
> +++ b/OvmfPkg/VirtioNetDxe/SnpGetStatus.c
> @@ -61,11 +61,15 @@ VirtioNetGetStatus (
>    OUT VOID                       **TxBuf OPTIONAL
>    )
>  {
> -  VNET_DEV   *Dev;
> -  EFI_TPL    OldTpl;
> -  EFI_STATUS Status;
> -  UINT16     RxCurUsed;
> -  UINT16     TxCurUsed;
> +  VNET_DEV             *Dev;
> +  EFI_TPL              OldTpl;
> +  EFI_STATUS           Status;
> +  UINT16               RxCurUsed;
> +  UINT16               TxCurUsed;
> +  EFI_PHYSICAL_ADDRESS DeviceAddress;
> +  UINT32               LocalInterruptStatus;
> +
> +  LocalInterruptStatus = *InterruptStatus;
>  
>    if (This == NULL) {
>      return EFI_INVALID_PARAMETER;
> @@ -113,11 +117,11 @@ VirtioNetGetStatus (
>      //
>      *InterruptStatus = 0;
>      if (Dev->RxLastUsed != RxCurUsed) {
> -      *InterruptStatus |= EFI_SIMPLE_NETWORK_RECEIVE_INTERRUPT;
> +      LocalInterruptStatus |= EFI_SIMPLE_NETWORK_RECEIVE_INTERRUPT;
>      }
>      if (Dev->TxLastUsed != TxCurUsed) {
>        ASSERT (Dev->TxCurPending > 0);
> -      *InterruptStatus |= EFI_SIMPLE_NETWORK_TRANSMIT_INTERRUPT;
> +      LocalInterruptStatus |= EFI_SIMPLE_NETWORK_TRANSMIT_INTERRUPT;
>      }
>    }
>  

I must have been unclear in my v2 review, sorry about that. My point was
that, given the changes that I requested in points v2/3 and v2/4, the
handling of "InterruptStatus" was fine as it was.

(1) Therefore please undo the v3 "InterruptStatus" changes -- the
"LocalInterruptStatus" variable is unnecessary.


> @@ -141,17 +145,36 @@ VirtioNetGetStatus (
>        ASSERT (DescIdx < (UINT32) (2 * Dev->TxMaxPending - 1));
>  
>        //
> -      // report buffer address to caller that has been enqueued by caller
> +      // get the device address that has been enqueued for the caller's
> +      // transmit buffer
>        //
> -      *TxBuf = (VOID *)(UINTN) Dev->TxRing.Desc[DescIdx + 1].Addr;
> +      DeviceAddress = Dev->TxRing.Desc[DescIdx + 1].Addr;
>  
>        //
>        // now this descriptor can be used again to enqueue a transmit buffer
>        //
>        Dev->TxFreeStack[--Dev->TxCurPending] = (UINT16) DescIdx;
> +
> +      //
> +      // Unmap the device address and perform the reverse mapping to find the
> +      // caller buffer address.
> +      //
> +      Status = VirtioNetUnmapTxBuf (
> +                 Dev,
> +                 TxBuf,
> +                 DeviceAddress
> +                 );
> +      if (EFI_ERROR (Status)) {
> +        //
> +        // VirtioNetUnmapTxBuf should never fail, if we have reached here
> +        // that means our internal state has been corrupted
> +        //
> +        ASSERT (FALSE);

The rest of VirtioNetGetStatus() looks good, but here's the other
misunderstanding:

(2) Please *keep* the ASSERT() that you are adding above, and below it,
*add back* what you had in v2:

        Status = EFI_DEVICE_ERROR;
        goto Exit;

The rest looks good.

Can you submit v4 soon please? :)

Thanks,
Laszlo

> +      }
>      }
>    }
>  
> +  *InterruptStatus = LocalInterruptStatus;
>    Status = EFI_SUCCESS;
>  
>  Exit:
> diff --git a/OvmfPkg/VirtioNetDxe/SnpTransmit.c b/OvmfPkg/VirtioNetDxe/SnpTransmit.c
> index 7ca40d5d0650..b39226e138b9 100644
> --- a/OvmfPkg/VirtioNetDxe/SnpTransmit.c
> +++ b/OvmfPkg/VirtioNetDxe/SnpTransmit.c
> @@ -73,11 +73,12 @@ VirtioNetTransmit (
>    IN UINT16                      *Protocol OPTIONAL
>    )
>  {
> -  VNET_DEV   *Dev;
> -  EFI_TPL    OldTpl;
> -  EFI_STATUS Status;
> -  UINT16     DescIdx;
> -  UINT16     AvailIdx;
> +  VNET_DEV              *Dev;
> +  EFI_TPL               OldTpl;
> +  EFI_STATUS            Status;
> +  UINT16                DescIdx;
> +  UINT16                AvailIdx;
> +  EFI_PHYSICAL_ADDRESS  DeviceAddress;
>  
>    if (This == NULL || BufferSize == 0 || Buffer == NULL) {
>      return EFI_INVALID_PARAMETER;
> @@ -144,10 +145,24 @@ VirtioNetTransmit (
>    }
>  
>    //
> +  // Map the transmit buffer system physical address to device address.
> +  //
> +  Status = VirtioNetMapTxBuf (
> +             Dev,
> +             Buffer,
> +             BufferSize,
> +             &DeviceAddress
> +             );
> +  if (EFI_ERROR (Status)) {
> +    Status = EFI_DEVICE_ERROR;
> +    goto Exit;
> +  }
> +
> +  //
>    // virtio-0.9.5, 2.4.1 Supplying Buffers to The Device
>    //
>    DescIdx = Dev->TxFreeStack[Dev->TxCurPending++];
> -  Dev->TxRing.Desc[DescIdx + 1].Addr  = (UINTN) Buffer;
> +  Dev->TxRing.Desc[DescIdx + 1].Addr  = DeviceAddress;
>    Dev->TxRing.Desc[DescIdx + 1].Len   = (UINT32) BufferSize;
>  
>    //
>