Re: [PATCH v3 12/23] OvmfPkg/VirtioRngDxe: map host address to device address

[Laszlo Ersek <lersek@redhat.com>]

On 08/23/17 14:22, Brijesh Singh wrote:
> patch maps the host address to a device address for buffers (including
> rings, device specifc request and response pointed by vring descriptor,
> and any further memory reference by those request and response).
> 
> 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/VirtioRngDxe/VirtioRng.h |  1 +
>  OvmfPkg/VirtioRngDxe/VirtioRng.c | 82 +++++++++++++++++---
>  2 files changed, 74 insertions(+), 9 deletions(-)
> 
> diff --git a/OvmfPkg/VirtioRngDxe/VirtioRng.h b/OvmfPkg/VirtioRngDxe/VirtioRng.h
> index 998f9fae48c2..389c8ddc8d31 100644
> --- a/OvmfPkg/VirtioRngDxe/VirtioRng.h
> +++ b/OvmfPkg/VirtioRngDxe/VirtioRng.h
> @@ -38,6 +38,7 @@ typedef struct {
>    EFI_EVENT                 ExitBoot;       // DriverBindingStart   0
>    VRING                     Ring;           // VirtioRingInit       2
>    EFI_RNG_PROTOCOL          Rng;            // VirtioRngInit        1
> +  VOID                      *RingMap;       // VirtioRingMap        2
>  } VIRTIO_RNG_DEV;
>  
>  #define VIRTIO_ENTROPY_SOURCE_FROM_RNG(RngPointer) \
> diff --git a/OvmfPkg/VirtioRngDxe/VirtioRng.c b/OvmfPkg/VirtioRngDxe/VirtioRng.c
> index 0abca488e6cd..59f32d343179 100644
> --- a/OvmfPkg/VirtioRngDxe/VirtioRng.c
> +++ b/OvmfPkg/VirtioRngDxe/VirtioRng.c
> @@ -140,6 +140,8 @@ VirtioRngGetRNG (
>    UINT32                    Len;
>    UINT32                    BufferSize;
>    EFI_STATUS                Status;
> +  EFI_PHYSICAL_ADDRESS      DeviceAddress;
> +  VOID                      *Mapping;
>  
>    if (This == NULL || RNGValueLength == 0 || RNGValue == NULL) {
>      return EFI_INVALID_PARAMETER;
> @@ -159,6 +161,20 @@ VirtioRngGetRNG (
>    }
>  
>    Dev = VIRTIO_ENTROPY_SOURCE_FROM_RNG (This);
> +  //
> +  // Map Buffer's system phyiscal address to device address
> +  //
> +  Status = VirtioMapAllBytesInSharedBuffer (
> +             Dev->VirtIo,
> +             VirtioOperationBusMasterWrite,
> +             (VOID *)Buffer,
> +             RNGValueLength,
> +             &DeviceAddress,
> +             &Mapping
> +             );
> +  if (EFI_ERROR (Status)) {
> +    goto FreeBuffer;
> +  }

(1) Sorry, I missed this in my previous review:

According to the interface contract of this protocol member function, we
should set Status to EFI_DEVICE_ERROR here, before jumping to the
FreeBuffer label. (Both old code, and new code other than this, do it.)

I can fix this up.

With that:

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

Thanks,
Laszlo

>  
>    //
>    // The Virtio RNG device may return less data than we asked it to, and can
> @@ -170,7 +186,7 @@ VirtioRngGetRNG (
>  
>      VirtioPrepare (&Dev->Ring, &Indices);
>      VirtioAppendDesc (&Dev->Ring,
> -      (UINTN)Buffer + Index,
> +      DeviceAddress + Index,
>        BufferSize,
>        VRING_DESC_F_WRITE,
>        &Indices);
> @@ -178,17 +194,35 @@ VirtioRngGetRNG (
>      if (VirtioFlush (Dev->VirtIo, 0, &Dev->Ring, &Indices, &Len) !=
>          EFI_SUCCESS) {
>        Status = EFI_DEVICE_ERROR;
> -      goto FreeBuffer;
> +      goto UnmapBuffer;
>      }
>      ASSERT (Len > 0);
>      ASSERT (Len <= BufferSize);
>    }
>  
> +  //
> +  // Unmap the device buffer before accessing it.
> +  //
> +  Status = Dev->VirtIo->UnmapSharedBuffer (Dev->VirtIo, Mapping);
> +  if (EFI_ERROR (Status)) {
> +    Status = EFI_DEVICE_ERROR;
> +    goto FreeBuffer;
> +  }
> +
>    for (Index = 0; Index < RNGValueLength; Index++) {
>      RNGValue[Index] = Buffer[Index];
>    }
>    Status = EFI_SUCCESS;
>  
> +UnmapBuffer:
> +  //
> +  // If we are reached here due to the error then unmap the buffer otherwise
> +  // the buffer is already unmapped after VirtioFlush().
> +  //
> +  if (EFI_ERROR (Status)) {
> +    Dev->VirtIo->UnmapSharedBuffer (Dev->VirtIo, Mapping);
> +  }
> +
>  FreeBuffer:
>    FreePool ((VOID *)Buffer);
>    return Status;
> @@ -205,6 +239,7 @@ VirtioRngInit (
>    EFI_STATUS Status;
>    UINT16     QueueSize;
>    UINT64     Features;
> +  UINT64     RingBaseShift;
>  
>    //
>    // Execute virtio-0.9.5, 2.2.1 Device Initialization Sequence.
> @@ -282,25 +317,42 @@ VirtioRngInit (
>    }
>  
>    //
> +  // If anything fails from here on, we must release the ring resources.
> +  //
> +  Status = VirtioRingMap (
> +             Dev->VirtIo,
> +             &Dev->Ring,
> +             &RingBaseShift,
> +             &Dev->RingMap
> +             );
> +  if (EFI_ERROR (Status)) {
> +    goto ReleaseQueue;
> +  }
> +
> +  //
>    // Additional steps for MMIO: align the queue appropriately, and set the
> -  // size. If anything fails from here on, we must release the ring resources.
> +  // size. If anything fails from here on, we must unmap the ring resources.
>    //
>    Status = Dev->VirtIo->SetQueueNum (Dev->VirtIo, QueueSize);
>    if (EFI_ERROR (Status)) {
> -    goto ReleaseQueue;
> +    goto UnmapQueue;
>    }
>  
>    Status = Dev->VirtIo->SetQueueAlign (Dev->VirtIo, EFI_PAGE_SIZE);
>    if (EFI_ERROR (Status)) {
> -    goto ReleaseQueue;
> +    goto UnmapQueue;
>    }
>  
>    //
>    // step 4c -- Report GPFN (guest-physical frame number) of queue.
>    //
> -  Status = Dev->VirtIo->SetQueueAddress (Dev->VirtIo, &Dev->Ring, 0);
> +  Status = Dev->VirtIo->SetQueueAddress (
> +                          Dev->VirtIo,
> +                          &Dev->Ring,
> +                          RingBaseShift
> +                          );
>    if (EFI_ERROR (Status)) {
> -    goto ReleaseQueue;
> +    goto UnmapQueue;
>    }
>  
>    //
> @@ -310,7 +362,7 @@ VirtioRngInit (
>      Features &= ~(UINT64)VIRTIO_F_VERSION_1;
>      Status = Dev->VirtIo->SetGuestFeatures (Dev->VirtIo, Features);
>      if (EFI_ERROR (Status)) {
> -      goto ReleaseQueue;
> +      goto UnmapQueue;
>      }
>    }
>  
> @@ -320,7 +372,7 @@ VirtioRngInit (
>    NextDevStat |= VSTAT_DRIVER_OK;
>    Status = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);
>    if (EFI_ERROR (Status)) {
> -    goto ReleaseQueue;
> +    goto UnmapQueue;
>    }
>  
>    //
> @@ -331,6 +383,9 @@ VirtioRngInit (
>  
>    return EFI_SUCCESS;
>  
> +UnmapQueue:
> +  Dev->VirtIo->UnmapSharedBuffer (Dev->VirtIo, Dev->RingMap);
> +
>  ReleaseQueue:
>    VirtioRingUninit (Dev->VirtIo, &Dev->Ring);
>  
> @@ -359,6 +414,9 @@ VirtioRngUninit (
>    // the old comms area.
>    //
>    Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, 0);
> +
> +  Dev->VirtIo->UnmapSharedBuffer (Dev->VirtIo, Dev->RingMap);
> +
>    VirtioRingUninit (Dev->VirtIo, &Dev->Ring);
>  }
>  
> @@ -385,6 +443,12 @@ VirtioRngExitBoot (
>    //
>    Dev = Context;
>    Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, 0);
> +
> +  //
> +  // Unmap the ring buffer so that hypervisor will not be able to get readable
> +  // data after device reset.
> +  //
> +  Dev->VirtIo->UnmapSharedBuffer (Dev->VirtIo, Dev->RingMap);
>  }
>  
>  
>