On Fri, Aug 02, 2019 at 09:45:15AM -0700, Gurchetan Singh wrote: > On Wed, Jul 31, 2019 at 11:40 PM Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote: > > > > On Wed, Jul 31, 2019 at 07:25:13PM -0700, Gurchetan Singh wrote: > > > The main use for udmabuf is sending guest memory pages > > > to the host. > > > > > > It's generally a bad idea to have to separate mappings with > > > different attributes. For example, a WC mapping the guest > > > kernel and cached mapping on the host is problematic. > > > > > > Add creation time flags so the user has responsibility for > > > the specific use case. > > > > > -#define UDMABUF_FLAGS_CLOEXEC 0x01 > > > +#define UDMABUF_FLAGS_CLOEXEC 0x01 > > > +#define UDMABUF_FLAGS_PROT_NONE 0x02 > > > +#define UDMABUF_FLAGS_PROT_READ 0x04 > > > +#define UDMABUF_FLAGS_PROT_WRITE 0x08 > > > > [ didn't look at followup patches yet ] > > > > You can't have readonly/writeonly dmabufs. > > So that isn't going to fly. > > > > The commit message suggests this is for cache attributes not protection, > > so having the flags might make sense, but please don't name the flags > > PROT_* then. > > Okay, I'll change the flags to CACHED / UNCACHED / WRITE_COMBINE (like > msm_drm.h). And since the dma api doesn't work on x86 [1], we'll have > to call drm_cflush_pages in the guest. Since caching is privileged on > ARM and not on x86, that *should* get us write-combine guest buffers. > > [1] https://lists.freedesktop.org/archives/dri-devel/2019-August/229161.html Ah, so you are aware of the vgem cache synchronization patches. It's probably a good idea to wait until that is finally settled before following with udmabuf. cheers, Gerd _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
