Hi Bharat, Could you Cc me on your next posting? Unfortunately I don't have much hardware for testing this at the moment, but I might be able to help a little on the review.
On Mon, Mar 16, 2020 at 02:40:00PM +0530, Bharat Bhushan wrote: > > >>> First issue is: your guest can use 4K page and your host can use 64KB > > >>> pages. In that case VFIO_DMA_MAP will fail with -EINVAL. We must devise > > >>> a way to pass the host settings to the VIRTIO-IOMMU device. > > >>> > > >>> Even with 64KB pages, it did not work for me. I have obviously not the > > >>> storm of VFIO_DMA_MAP failures but I have some, most probably due to > > >>> some wrong notifications somewhere. I will try to investigate on my > > >>> side. > > >>> > > >>> Did you test with VFIO on your side? > > >> > > >> I did not tried with different page sizes, only tested with 4K page size. > > >> > > >> Yes it works, I tested with two n/w device assigned to VM, both > > >> interfaces works > > >> > > >> First I will try with 64k page size. > > > > > > 64K page size does not work for me as well, > > > > > > I think we are not passing correct page_size_mask here > > > (config.page_size_mask is set to TARGET_PAGE_MASK ( which is > > > 0xfffffffffffff000)) > > I guess you mean with guest using 4K and host using 64K. > > > > > > We need to set this correctly as per host page size, correct? > > Yes that's correct. We need to put in place a control path to retrieve > > the page settings on host through VFIO to inform the virtio-iommu device. > > > > Besides this issue, did you try with 64kB on host and guest? > > I tried Followings > - 4k host and 4k guest - it works with v7 version > - 64k host and 64k guest - it does not work with v7 > hard-coded config.page_size_mask to 0xffffffffffff0000 and it works You might get this from the iova_pgsize bitmap returned by VFIO_IOMMU_GET_INFO. The virtio config.page_size_mask is global so there is the usual problem of aggregating consistent properties, but I'm guessing using the host page size as a granule here is safe enough. If it is a problem, we can add a PROBE property for page size mask, allowing to define per-endpoint page masks. I have kernel patches somewhere to do just that. Thanks, Jean
