Re: [PATCH v3 4/8] OvmfPkg/VirtioNetDxe: dynamically alloc transmit header

[Laszlo Ersek <lersek@redhat.com>]

On 09/14/17 13:08, Brijesh Singh wrote:
> Each network packet is submitted for transmission by pushing the head
> descriptor of a two-part descriptor chain to the Available Ring of the
> TX queue. VirtioNetInitTx() sets up the the descriptor chains for all
> queueable packets in advance, and points all the head descriptors to the
> same shared, never modified, VIRTIO_1_0_NET_REQ header object (or its
> initial VIRTIO_NET_REQ sub-object, dependent on virtio version).
> VirtioNetInitTx() currently uses the header object's system physical
> address for populating the head descriptors.
> 
> When device is behind the IOMMU, VirtioNet driver is required to provide
> the device address of VIRTIO_1_0_NET_REQ header. In this patch we
> dynamically allocate the header using AllocateSharedPages() and map with
> BusMasterCommonBuffer so that header can be accessed by both processor
> and the device.
> 
> We map the header object for CommonBuffer operation because, in order to
> stick with the current code order, we populate the head descriptors with
> the header's device address first, and fill in the header itself second.
> 
> 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/VirtioNet.h        |  3 +-
>  OvmfPkg/VirtioNetDxe/SnpInitialize.c    | 64 +++++++++++++++++---
>  OvmfPkg/VirtioNetDxe/SnpSharedHelpers.c |  7 +++
>  3 files changed, 65 insertions(+), 9 deletions(-)

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