[PATCH V3 vfio 2/7] virtio: Extend the admin command to include the result size

[Yishai Hadas]

Extend the admin command by incorporating a result size field.

This allows higher layers to determine the actual result size from the
backend when this information is not included in the result_sg.

The additional information introduced here will be used in subsequent
patches of this series.

Acked-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Yishai Hadas <yish...@nvidia.com>
---
 drivers/virtio/virtio_pci_modern.c | 4 +++-
 include/linux/virtio.h             | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_pci_modern.c 
b/drivers/virtio/virtio_pci_modern.c
index 9193c30d640a..487d04610ecb 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -64,8 +64,10 @@ void vp_modern_avq_done(struct virtqueue *vq)
        spin_lock_irqsave(&admin_vq->lock, flags);
        do {
                virtqueue_disable_cb(vq);
-               while ((cmd = virtqueue_get_buf(vq, &len)))
+               while ((cmd = virtqueue_get_buf(vq, &len))) {
+                       cmd->result_sg_size = len;
                        complete(&cmd->completion);
+               }
        } while (!virtqueue_enable_cb(vq));
        spin_unlock_irqrestore(&admin_vq->lock, flags);
 }
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 306137a15d07..b5f7a611715a 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -111,6 +111,7 @@ struct virtio_admin_cmd {
        struct scatterlist *data_sg;
        struct scatterlist *result_sg;
        struct completion completion;
+       u32 result_sg_size;
        int ret;
 };
 
-- 
2.27.0