Hi Peter, On 13/12/17 07:49, Peter Xu wrote: > On Tue, Dec 12, 2017 at 12:59:39PM -0700, Alex Williamson wrote: >> The vfio_info_add_capability() helper requires the caller to pass a >> capability ID, which it then uses to fill in header fields, assuming >> hard coded versions. This makes for an awkward and rigid interface. >> The only thing we want this helper to do is allocate sufficient >> space in the caps buffer and chain this capability into the list. >> Reduce it to that simple task. >> >> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> > > Reviewed-by: Peter Xu <peterx@xxxxxxxxxx> > > Though during review I had a question related to the function > msix_sparse_mmap_cap(): Is it possible that one PCI device BAR is very > small (e.g., 4K) that only contains the MSI-X table (and another small > PBA area)? If so, should we just mark that region unmappable instead > of setting vfio_region_info_cap_sparse_mmap.nr_areas to 1 in > msix_sparse_mmap_cap()? > > /* If MSI-X table is aligned to the start or end, only one area */ > if (((vdev->msix_offset & PAGE_MASK) == 0) || > (PAGE_ALIGN(vdev->msix_offset + vdev->msix_size) >= end)) > nr_areas = 1; > > Thanks, > if I understand the code correctly, if the MSI-X table exactly matches the BAR, a sparse mmap region is reported with offset/size = 0. Is that correct? Thanks Eric
