? 2021/4/22 ??2:31, Christoph Hellwig ??:> On Wed, Apr 21, 2021 at 11:21:10AM +0800, Jason Wang wrote: >> The behaivor for non DMA API is kept for minimizing the performance >> impact. > NAK. Everyone should be using the DMA API in a modern world. So > treating the DMA API path worse than the broken legacy path does not > make any sense whatsoever.I think the goal is not treat DMA API path worse than legacy. The issue is that the management layer should guarantee that ACCESS_PLATFORM is set so DMA API is guaranteed to be used by the driver. So I'm not sure how much value we can gain from trying to 'fix' the legacy path. But I can change the behavior of legacy path to match DMA API path. Thanks
Michael S. Tsirkin
2021-Apr-23 20:14 UTC
[RFC PATCH 0/7] Untrusted device support for virtio
On Thu, Apr 22, 2021 at 04:19:16PM +0800, Jason Wang wrote:> > ? 2021/4/22 ??2:31, Christoph Hellwig ??: > > On Wed, Apr 21, 2021 at 11:21:10AM +0800, Jason Wang wrote: > > > The behaivor for non DMA API is kept for minimizing the performance > > > impact. > > NAK. Everyone should be using the DMA API in a modern world. So > > treating the DMA API path worse than the broken legacy path does not > > make any sense whatsoever. > > > I think the goal is not treat DMA API path worse than legacy. The issue is > that the management layer should guarantee that ACCESS_PLATFORM is set so > DMA API is guaranteed to be used by the driver. So I'm not sure how much > value we can gain from trying to 'fix' the legacy path. But I can change the > behavior of legacy path to match DMA API path. > > ThanksI think before we maintain different paths with/without ACCESS_PLATFORM it's worth checking whether it's even a net gain. Avoiding sharing by storing data in private memory can actually turn out to be a net gain even without DMA API. It is worth checking what is the performance effect of this patch. -- MST