Xuan Zhuo
2023-Apr-11 07:23 UTC
[PATCH vhost v6 08/11] virtio_ring: introduce virtqueue_dma_dev()
On Mon, 10 Apr 2023 23:45:33 -0700, Christoph Hellwig <hch at infradead.org> wrote:> On Tue, Apr 11, 2023 at 02:33:29PM +0800, Xuan Zhuo wrote: > > Do you mean my idea is wrong, right? > > > > Can you explain it? Why can't we support a device that uses only dirct map? > > If a direct map or not is used is a decision done by the platform code, > often based on firmware tables. You can't just override that.Can Virtio Device set its own dma_ops? It is a device on the virtual bus. It sets its own DMA_OPS. I think it is reasonable. Thanks.
Christoph Hellwig
2023-Apr-11 12:16 UTC
[PATCH vhost v6 08/11] virtio_ring: introduce virtqueue_dma_dev()
On Tue, Apr 11, 2023 at 03:23:43PM +0800, Xuan Zhuo wrote:> > If a direct map or not is used is a decision done by the platform code, > > often based on firmware tables. You can't just override that. > > > Can Virtio Device set its own dma_ops? It is a device on the virtual bus. It > sets its own DMA_OPS. I think it is reasonable.No, it can't. virtio devices are backed by PCI, platform or other bus devices, and the (often virtual) firmware controls how DMA mapping is to be performed for them, at least for the platform_access case.