Re: [PATCH] xen: introduce xen_vring_use_dma

["Michael S. Tsirkin" <mst@xxxxxxxxxx>]

On Wed, Jun 24, 2020 at 05:17:32PM +0800, Peng Fan wrote:
> Export xen_swiotlb for all platforms using xen swiotlb
> 
> Use xen_swiotlb to determine when vring should use dma APIs to map the
> ring: when xen_swiotlb is enabled the dma API is required. When it is
> disabled, it is not required.
> 
> Signed-off-by: Peng Fan <peng.fan@xxxxxxx>

Isn't there some way to use VIRTIO_F_IOMMU_PLATFORM for this?
Xen was there first, but everyone else is using that now.


> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index a2de775801af..768afd79f67a 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -252,7 +252,7 @@ static bool vring_use_dma_api(struct virtio_device *vdev)
>        * the DMA API if we're a Xen guest, which at least allows
>        * all of the sensible Xen configurations to work correctly.
>        */
> -     if (xen_domain())
> +     if (xen_vring_use_dma())
>               return true;
>  
>       return false;


The comment above this should probably be fixed.

-- 
MST