On Mon, Sep 18, 2023 at 05:37:47PM +0100, Robin Murphy wrote: > > diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c > > index 17dcd826f5c2..3649586f0e5c 100644 > > --- a/drivers/iommu/virtio-iommu.c > > +++ b/drivers/iommu/virtio-iommu.c > > @@ -189,6 +189,12 @@ static int viommu_sync_req(struct viommu_dev *viommu) > > int ret; > > unsigned long flags; > > + /* > > + * .iotlb_sync_map and .flush_iotlb_all may be called before the viommu > > + * is initialized e.g. via iommu_create_device_direct_mappings() > > + */ > > + if (!viommu) > > + return 0; > > Minor nit: I'd be inclined to make that check explicitly in the places where > it definitely is expected, rather than allowing *any* sync to silently do > nothing if called incorrectly. Plus then they could use > vdomain->nr_endpoints for consistency with the equivalent checks elsewhere > (it did take me a moment to figure out how we could get to .iotlb_sync_map > with a NULL viommu without viommu_map_pages() blowing up first...)
They're not strictly equivalent: this check works around a temporary issue with the IOMMU core, which calls map/unmap before the domain is finalized. Once we merge domain_alloc() and finalize(), then this check disappears, but we still need to test nr_endpoints in map/unmap to handle detached domains (and we still need to fix the synchronization of nr_endpoints against attach/detach). That's why I preferred doing this on viommu and keeping it in one place. Thanks, Jean _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
