On Tue, 3 Sep 2024 21:43:48 +0200 Simona Vetter <simona.vetter@xxxxxxxx> wrote: > On Thu, Feb 29, 2024 at 05:22:24PM +0100, Boris Brezillon wrote: > > - Add our job fence as DMA_RESV_USAGE_WRITE to all external objects > > (was previously DMA_RESV_USAGE_BOOKKEEP). I don't get why, given > > we're supposed to be fully-explicit, but other drivers do that, so > > there must be a good reason > > Just spotted this: They're wrong, or they're userspace is broken and > doesn't use the dma_buf fence import/export ioctl in all the right places. > For gl this simplifies things (but setting write fences when you're only > reading is still bad, and setting fences on buffers you don't even touch > is worse), for vulkan this is just bad. For the record, I remember pointing that out in some drm_sched discussion, and being told that this was done on purpose :-/. > > I think you want a context creation flag for userspace that's not broken, > which goes back to USAGE_BOOKKEEP for everything. Honestly, given the only user (the gallium driver) is already designed to do the explicit <-> implicit dance, and the fact the driver just got merged in the last release, I'd rather go for a silent USAGE_WRITE -> USAGE_BOOKKEEP if things keep working with that.
