Messages in this thread | | | Date | Thu, 3 May 2018 21:26:47 +0800 | From | Tiwei Bie <> | Subject | Re: [RFC] virtio: support VIRTIO_F_IO_BARRIER |
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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@intel.com> > > 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
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