On Thu, Jan 8, 2026 at 7:42 AM Alex Williamson <[email protected]> wrote: > > On Wed, 7 Jan 2026 19:36:44 -0800 > Alex Mastro <[email protected]> wrote: > > On Wed, Jan 07, 2026 at 11:54:09PM +0000, David Matlack wrote: > > > > > > Speaking of, maybe we can add a test that creating writable IOMMU > > > mappings fails for read-only BARs? > > > > I think I'll have to look into this as a follow-on. I'm not sure how to > > validate > > it yet without mocks or similar since I don't have such HW. > > I think the read-only aspect would be in the mmap, not the BAR itself, > ie. can we create a read-write DMA mapping to a read-only mmap.
Good point. So it'd be better to have a test of that in vfio_dma_mapping_test. No need to use a BAR mapping. > ROM BARs are the only BARs that are read-only, but they can share a > decoder with the standard BARs and therefore have a separate enable in > the BAR register itself. Due to this, and their general usage, it's > never been necessary to allow mmap of the ROM BAR, therefore we cannot > actually DMA map the ROM BAR. Thanks, Ahh, good to know, thanks for the context!
