On Thu, Sep 02, 2021 at 05:05:05PM +0000, Bloomfield, Jon wrote: > > -----Original Message----- > > From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> > > Sent: Thursday, September 2, 2021 9:42 AM > > To: Daniel Vetter <daniel@xxxxxxxx> > > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>; DRI Development <dri- > > devel@xxxxxxxxxxxxxxxxxxxxx>; Intel Graphics Development <intel- > > gfx@xxxxxxxxxxxxxxxxxxxxx>; Maarten Lankhorst > > <maarten.lankhorst@xxxxxxxxxxxxxxx>; Vetter, Daniel > > <daniel.vetter@xxxxxxxxx>; Bloomfield, Jon <jon.bloomfield@xxxxxxxxx>; > > Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>; Joonas Lahtinen > > <joonas.lahtinen@xxxxxxxxxxxxxxx>; Thomas Hellström > > <thomas.hellstrom@xxxxxxxxxxxxxxx>; Auld, Matthew > > <matthew.auld@xxxxxxxxx>; Landwerlin, Lionel G > > <lionel.g.landwerlin@xxxxxxxxx>; Dave Airlie <airlied@xxxxxxxxxx>; Jason > > Ekstrand <jason@xxxxxxxxxxxxxx> > > Subject: Re: [Intel-gfx] [PATCH 07/11] drm/i915: Add > > i915_gem_context_is_full_ppgtt > > > > > > On 02/09/2021 16:22, Daniel Vetter wrote: > > > On Thu, Sep 02, 2021 at 03:54:36PM +0100, Tvrtko Ursulin wrote: > > >> On 02/09/2021 15:20, Daniel Vetter wrote: > > >>> And use it anywhere we have open-coded checks for ctx->vm that really > > >>> only check for full ppgtt. > > >>> > > >>> Plus for paranoia add a GEM_BUG_ON that checks it's really only set > > >>> when we have full ppgtt, just in case. gem_context->vm is different > > >>> since it's NULL in ggtt mode, unlike intel_context->vm or gt->vm, > > >>> which is always set. > > >>> > > >>> v2: 0day found a testcase that I missed. > > >>> > > >>> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > > >>> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > > >>> Cc: Jon Bloomfield <jon.bloomfield@xxxxxxxxx> > > >>> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > >>> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > > >>> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> > > >>> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> > > >>> Cc: "Thomas Hellström" <thomas.hellstrom@xxxxxxxxxxxxxxx> > > >>> Cc: Matthew Auld <matthew.auld@xxxxxxxxx> > > >>> Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx> > > >>> Cc: Dave Airlie <airlied@xxxxxxxxxx> > > >>> Cc: Jason Ekstrand <jason@xxxxxxxxxxxxxx> > > >>> --- > > >>> drivers/gpu/drm/i915/gem/i915_gem_context.c | 2 +- > > >>> drivers/gpu/drm/i915/gem/i915_gem_context.h | 7 +++++++ > > >>> drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 2 +- > > >>> drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c | 6 +++--- > > >>> 4 files changed, 12 insertions(+), 5 deletions(-) > > >>> > > >>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c > > b/drivers/gpu/drm/i915/gem/i915_gem_context.c > > >>> index 7a566fb7cca4..1eec85944c1f 100644 > > >>> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c > > >>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c > > >>> @@ -1566,7 +1566,7 @@ static int get_ppgtt(struct > > drm_i915_file_private *file_priv, > > >>> int err; > > >>> u32 id; > > >>> - if (!rcu_access_pointer(ctx->vm)) > > >>> + if (!i915_gem_context_is_full_ppgtt(ctx)) > > >> > > >> It reads a bit wrong because GEM context cannot *be* full ppggt. It can > > be > > >> associated with a VM which is or isn't full ppgtt. So a test on a VM > > >> retrieved from a context is semnntically more correct. Perhaps you want > > to > > >> consider adding a helper to that effect instead? It could mean splitting > > >> into two helpers (getter + test) or maybe just renaming would work. Like > > >> i915_gem_context_has_full_ppgtt_vm(ctx)? > > > > > > The pointer isn't set when the driver/context isn't running in full ppgtt > > > mode. This is why I've added the GEM_BUG_ON to check we're not > > breaking > > > any invariants. So yeah it is a full ppgtt context or it's not, that is > > > indeed the question here. > > > > > > I'm happy to bikeshed the naming, but I don't see how your suggestion is > > > an improvement. > > > > I think the pointer being set or not is implementation detail, for > > instance we could have it always set just like it is in intel_context. > > > > I simply think GEM context *isn't* full ppgtt, but the VM is. And since > > GEM context *points* to a VM, *has* is the right verb in my mind. You > > did not write why do you not see has as more correct than is so I don't > > want to be guessing too much. > > FWIW, I agree with Tvrtko. i915_gem_context_is_full_ppgtt is incorrect > grammar. It IS a bike shed, but, hey it'll live for a while. Generally all our feature checks are of the various is_foo variety. HAS_FULL_PPGTT is one of the very rare exceptions. So it's a question of "is gem_ctx foo", not "has gem_ctx foo". The fact that we implement the check by looking at a pointer doesn't matter. And yes if it is full ppgtt, it also has it's own private vm, but we don't care about that part at all. It's just a distraction. Anyway I'll repaint, least because the HAS_FULL_PPGTT thing is almost a decade old by now :-) -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
