Christoph Hellwig
2023-Jul-20 06:23 UTC
[PATCH vhost v11 10/10] virtio_net: merge dma operation for one page
Hi Jason, can you please resend your reply with proper quoting? I had to give up after multiple pages of scrolling without finding anything that you added to the full quote.
Jason Wang
2023-Jul-20 07:41 UTC
[PATCH vhost v11 10/10] virtio_net: merge dma operation for one page
On Thu, Jul 20, 2023 at 2:23?PM Christoph Hellwig <hch at infradead.org> wrote:> > Hi Jason, > > can you please resend your reply with proper quoting? I had to give > up after multiple pages of scrolling without finding anything that > you added to the full quote.I guess it's this part?> > > You should also test without iommu but with swiotlb=force > > > > > > For swiotlb, merge DMA has no benefit, because we still need to copy data from > > swiotlb buffer to the origin buffer. > > The benefit of the merge DMA is to reduce the operate to the iommu device. > > > > I did some test for this. The result is same. > > > > Thanks. > > > > Did you actually check that it works though? > Looks like with swiotlb you need to synch to trigger a copy > before unmap, and I don't see where it's done in the current > patch.And this is needed for XDP_REDIRECT as well. Thanks