On Tue, Apr 11, 2023 at 1:14 PM Christoph Hellwig <h...@infradead.org> wrote:
>
> On Tue, Apr 11, 2023 at 12:54:46PM +0800, Jason Wang wrote:
> > Ok, just to clarify, I meant there could be a case where the virtqueue
> > is emulated by software, in this case we need check whether the
> > virtqueue has a dma device or not in vring_use_dma_api(). If not we
> > need return false.
>
> Well, that's what vring_use_dma_api basically does.  Such devics
> just should never have VIRTIO_F_ACCESS_PLATFORM set.  If there is
> a really good reason for such a device to have VIRTIO_F_ACCESS_PLATFORM
> set we'd need an extra quirk in vring_use_dma_api indeed.
>

This is useful for some vDPA devices where the control virtqueue is
emulated by the vDPA parent (who will decode the control virtqueue
commands to vendor specific control commands).

Thanks

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