On Thu, May 3, 2018 at 2:26 PM, Tiwei Bie <tiwei.bie@xxxxxxxxx> wrote: > On Thu, May 03, 2018 at 10:06:52AM +0100, Stefan Hajnoczi wrote: >> On Thu, May 03, 2018 at 10:59:55AM +0800, Tiwei Bie wrote: >> > This patch introduces the support for VIRTIO_F_IO_BARRIER. >> > When this feature is negotiated, driver will use the barriers >> > suitable for hardware devices. >> > >> > Signed-off-by: Tiwei Bie <tiwei.bie@xxxxxxxxx> >> >> I should have thought of this earlier, but why is a new feature bit >> necessary? If a hardware virtio device is in use, then the device >> should already negotiate VIRTIO_F_IOMMU_PLATFORM (i.e. use DMA APIs and >> IOMMU callbacks). >> >> Does disabling weak_barriers when VIRTIO_F_IOMMU_PLATFORM is set solve >> the problem? > > The VIRTIO_F_IOMMU_PLATFORM feature can be set when the > device is implemented in software. And I think we don't > want the performance drop in this case. Good point. Stefan _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
