OvmfPkg/VirtioBlkDxe: Check the return status of unmap data buffer
OvmfPkg/VirtioBlkDxe: Check the return status of unmap data buffer

when "RequestIsWrite" is FALSE -- i.e., the CPU wants data from
the device, we map "Buffer" for VirtioOperationBusMasterWrite. In
this case, checking the return status of

Dev->VirtIo->UnmapSharedBuffer (Dev->VirtIo, BufferMapping);

is must. If the unmapping fails, then "Buffer" will not contain the
actual data from the device, and we must fail the request with
EFI_DEVICE_ERROR.

Cc: Ard Biesheuvel <66d3c5fdaeea7ff1f996ad04f2c45e08ab38e2f5@linaro.org>
Cc: Jordan Justen <a79006884ba9cf5f4f7fcbb92a15b208780d8c97@intel.com>
Cc: Tom Lendacky <bcbe2d8614c98cf419bfc4320d4a7a260d53de8f@amd.com>
Cc: Laszlo Ersek <7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Brijesh Singh <6c1ba716601dd19ee463759bfdaf6de1e69b2b21@amd.com>
[7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com: fix typos in subject]
Reviewed-by: Laszlo Ersek <7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com>
Tested-by: Laszlo Ersek <7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com>

MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2