On Thu, Mar 11, 2021 at 10:31 AM Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > > Quoting Zbigniew Kempczyński (2021-03-11 11:44:32) > > On Wed, Mar 10, 2021 at 03:50:07PM -0600, Jason Ekstrand wrote: > > > The Vulkan driver in Mesa for Intel hardware never uses relocations if > > > it's running on a version of i915 that supports at least softpin which > > > all versions of i915 supporting Gen12 do. On the OpenGL side, Gen12+ is > > > only supported by iris which never uses relocations. The older i965 > > > driver in Mesa does use relocations but it only supports Intel hardware > > > through Gen11 and has been deprecated for all hardware Gen9+. The > > > compute driver also never uses relocations. This only leaves the media > > > driver which is supposed to be switching to softpin going forward. > > > Making softpin a requirement for all future hardware seems reasonable. > > > > > > Rejecting relocations starting with Gen12 has the benefit that we don't > > > have to bother supporting it on platforms with local memory. Given how > > > much CPU touching of memory is required for relocations, not having to > > > do so on platforms where not all memory is directly CPU-accessible > > > carries significant advantages. > > > > > > v2 (Jason Ekstrand): > > > - Allow TGL-LP platforms as they've already shipped > > > > > > v3 (Jason Ekstrand): > > > - WARN_ON platforms with LMEM support in case the check is wrong > > > > I was asked to review of this patch. It works along with expected > > IGT check https://patchwork.freedesktop.org/patch/423361/?series=82954&rev=25 > > > > Before I'll give you r-b - isn't i915_gem_execbuffer2_ioctl() better place > > to do for loop just after copy_from_user() and check relocation_count? > > We have an access to exec2_list there, we know the gen so we're able to say > > relocations are not supported immediate, without entering i915_gem_do_execbuffer(). > > There's a NORELOC flag you can enforce as mandatory. That's trivial for > userspace to set, really makes sure they are aware of the change afoot, > and i915_gem_ceck_execbuffer() will perform the validation upfront with > the other flag checks. NORELOC doesn't quite ensure that there are no relocations; it just makes things optional if the kernel hasn't moved anything. I guess we could require userspace to set it but it also doesn't do anything if there are no relocations to begin with. I think I'd personally err on the side of not requiring pointless flags. --Jason _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
