On Thu, Mar 26, 2026 at 3:41 PM Keith Busch <[email protected]> wrote: > > > > On Wed, Mar 25, 2026 at 10:25:34AM +0200, Leon Romanovsky wrote: > > On Tue, Mar 24, 2026 at 04:46:02PM -0700, Zhiping Zhang wrote: > > > struct vfio_device_feature_dma_buf { > > > __u32 region_index; > > > __u32 open_flags; > > > - __u32 flags; > > > - __u32 nr_ranges; > > > + __u32 flags; > > > +#define VFIO_DMABUF_FL_TPH (1U << 0) /* TPH info is present */ > > > +#define VFIO_DMABUF_TPH_PH_SHIFT 1 /* bits 1-2: PH (2-bit) */ > > > +#define VFIO_DMABUF_TPH_PH_MASK 0x6U > > > +#define VFIO_DMABUF_TPH_ST_SHIFT 16 /* bits 16-31: steering tag > > > */ > > > +#define VFIO_DMABUF_TPH_ST_MASK 0xffff0000U > > > > This extension of flags is basically kills future extension of this > > struct for anything that includes TPH. > > > > Add new > > enum vfio_device_feature_dma_buf_flags { > > VFIO_DMABUF_FL_TPH = 1 << 0 > > }
yes we can do that. > > > > > + __u32 nr_ranges; > > > > add your "__u16 steering_tag" and "__u8 ph" fields here. > That is what I did in V1, Leon. > You're suggesting that Ziping append the new fields to the end of this > struct? I don't think we can modify the layout of a uapi. > > If we can't carve the space for this out of the existing unused flags > field, I think we'd have to introduce a new vfio device feature that > basically copies VFIO_DEVICE_FEATURE_DMA_BUF with the extra hints > fields. > if not using the fields in the flag, then we probably have to introduce a new vfio device feature. > > > struct vfio_region_dma_range dma_ranges[] __counted_by(nr_ranges); > > > };
