Re: [PATCH v4 17/21] iommu/riscv: Report cache coherency capability
Jason Gunthorpe <[email protected]>
| Newsgroups | dev.linux.lists.iommu,org.infradead.lists.linux-riscv,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
On Thu, Aug 20, 2026 at 11:41:46PM +0200, Andrew Jones wrote: > VFIO and iommufd require IOMMU_CAP_CACHE_COHERENCY because they use > IOMMU_CACHE mappings and have no userspace cache-maintenance path. > > RISC-V page tables preserve physical memory attributes for IOMMU_CACHE > mappings. Svpbmt marks mappings without IOMMU_CACHE as non-cacheable, > but preserving physical attributes cannot make a noncoherent device > path coherent. > > Report the capability only for devices marked DMA coherent. This limits > userspace assignment to paths that can honor cacheable mappings. > > Signed-off-by: Andrew Jones <[email protected]> > --- > drivers/iommu/riscv/iommu.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) Reviewed-by: Jason Gunthorpe <[email protected]> You can send this outside this series? Jason