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charset="utf-8" From: Manish Honap vfio_container_region_add() attempts an IOMMU DMA mapping for every RAM section that enters the guest address space. For VFIO mmap-backed regions (PCI BAR windows, CXL.mem regions), this mapping always fails: the backing VMAs carry VM_IO | VM_PFNMAP flags and pin_user_pages() refuses to pin VM_IO pages, so IOMMU_IOAS_MAP returns -EFAULT. CPU access to these regions goes through KVM Stage-2 page faults independently of the SMMU/IOMMU, so no IOMMU entry is required for correct operation. Add an early return for RAM-device sections owned by a VFIO device. vfio_get_vfio_device(memory_region_owner(section->mr)) returns non-NULL for any mmap subregion created by vfio_region_mmap(), since memory_region_init_ram_device_ptr() propagates the VFIOPCIDevice owner from the containing region. Matching on ownership covers both normal PCI BAR windows and CXL.mem regions uniformly; non-VFIO RAM-device regions such as NVDIMMs are unaffected and continue through the normal mapping path. Signed-off-by: Manish Honap --- hw/vfio/listener.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/hw/vfio/listener.c b/hw/vfio/listener.c index 31c3113f8f..46cad18357 100644 --- a/hw/vfio/listener.c +++ b/hw/vfio/listener.c @@ -608,6 +608,20 @@ void vfio_container_region_add(VFIOContainer *bcontain= er, pgmask + 1); return; } + + /* + * VFIO MMAP backed regions (CXL.mem) uses VM_IO | VM_PFNMAP VMAs + * backed by physical device addresses. Skip vfio_container_dma_map + * as mapping is not needed for this region. + */ + if (vfio_get_vfio_device(memory_region_owner(section->mr))) { + trace_vfio_listener_region_add_no_dma_map( + memory_region_name(section->mr), + section->offset_within_address_space, + int128_getlo(section->size), + pgmask + 1); + return; + } } =20 ret =3D vfio_container_dma_map(bcontainer, iova, int128_get64(llsize), --=20 2.25.1