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. Best regards, Tiwei Bie _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
