On Mon, Nov 11, 2024 at 04:36:52PM +0800, Jason Wang wrote: > On Mon, Nov 11, 2024 at 3:30 PM Michael S. Tsirkin <[email protected]> wrote: > > > > On Mon, Nov 11, 2024 at 10:55:38AM +0800, Jason Wang wrote: > > > There's no need to sync DMA for CPU on mapping errors. So this patch > > > skips the CPU sync in the error handling path of DMA mapping. > > > > > > Signed-off-by: Jason Wang <[email protected]> > > > > DMA sync is idempotent. > > Extra work for slow path. Why do we bother? > > dma_map_sg() did this, since current virtio hack sg mappings to per > page mapping, we lose such optimization. > > Actually the path is not necessarily slowpath in some setups like > swiotlb or VDUSE. > > Thanks
I don't get how it's not a slowpath. Example? -- MST
