On 2022-07-14 12:11, Jean-Philippe Brucker wrote:
Fix virtio-iommu interaction with VFIO, as VFIO now requires IOMMU_CAP_CACHE_COHERENCY. virtio-iommu does not support non-cacheable mappings, and always expects to be called with IOMMU_CACHE.
Can we know this is actually true though? What if the virtio-iommu implementation is backed by something other than VFIO, and the underlying hardware isn't coherent? AFAICS the spec doesn't disallow that.
Thanks, Robin.
Fixes: e8ae0e140c05 ("vfio: Require that devices support DMA cache coherence") Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> --- drivers/iommu/virtio-iommu.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c index 25be4b822aa0..bf340d779c10 100644 --- a/drivers/iommu/virtio-iommu.c +++ b/drivers/iommu/virtio-iommu.c @@ -1006,7 +1006,18 @@ static int viommu_of_xlate(struct device *dev, struct of_phandle_args *args) return iommu_fwspec_add_ids(dev, args->args, 1); }+static bool viommu_capable(enum iommu_cap cap)+{ + switch (cap) { + case IOMMU_CAP_CACHE_COHERENCY: + return true; + default: + return false; + } +} + static struct iommu_ops viommu_ops = { + .capable = viommu_capable, .domain_alloc = viommu_domain_alloc, .probe_device = viommu_probe_device, .probe_finalize = viommu_probe_finalize,
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