From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 23B89C33CB1 for ; Wed, 15 Jan 2020 15:35:58 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D7E7A222C3 for ; Wed, 15 Jan 2020 15:35:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D7E7A222C3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 769B36EA2E; Wed, 15 Jan 2020 15:35:57 +0000 (UTC) Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id 71C1B6EA2E for ; Wed, 15 Jan 2020 15:35:56 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from localhost (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP (TLS) id 19890410-1500050 for multiple; Wed, 15 Jan 2020 15:35:42 +0000 MIME-Version: 1.0 From: Chris Wilson User-Agent: alot/0.6 To: Intel-gfx@lists.freedesktop.org, Tvrtko Ursulin References: <20200115152437.13207-1-tvrtko.ursulin@linux.intel.com> In-Reply-To: Message-ID: <157910253984.14122.1935242870824479556@skylake-alporthouse-com> Date: Wed, 15 Jan 2020 15:35:39 +0000 Subject: Re: [Intel-gfx] [PATCH] drm/i915: Align engine->uabi_class/instance with i915_drm.h X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Quoting Tvrtko Ursulin (2020-01-15 15:28:19) > > On 15/01/2020 15:24, Tvrtko Ursulin wrote: > > From: Tvrtko Ursulin > > > > In our ABI we have defined I915_ENGINE_CLASS_INVALID_NONE and > > I915_ENGINE_CLASS_INVALID_VIRTUAL as negative values which creates > > implicit coupling with type widths used in, also ABI, struct > > i915_engine_class_instance. > > > > When for instance we export engine->uabi_class > > I915_ENGINE_CLASS_INVALID_VIRTUAL from our our tracepoints, because the > > type of the former is u8 in contrast to u16 defined in the ABI, 254 will > > be returned instead of 65534 which userspace would legitimately expect. > > > > Therefore we need to align the type used to store engine ABI class and > > instance. > > > > I did not find any other user visible inconsistency apart from the > > tracepoints so I think importance of the fix is low. > > Alternatives: > > 1. > Embed struct i915_engine_class_instance in struct intel_engine_cs, but > downside is more churn. Could do. It would seem to make sense. > 2. > Only tweak the tracepoints to cast back and forth, but is it possible to > cast from unsigned to signed and get a negative number? > > 3. > Do nothing, does anyone cares? It actually changes the value reported by GET_ENGINES for a virtual engine, right? engine->uabi_instance is u8, so u16 ci.engine_instance = engine->uabi_instance is zero extended, not sign extended. And we did say that is expected to be (u16)-2 already. So cc:stable > > Signed-off-by: Tvrtko Ursulin > > Cc: Chris Wilson Reviewed-by: Chris Wilson > > --- > > drivers/gpu/drm/i915/gem/i915_gem_busy.c | 12 ++++++------ > > drivers/gpu/drm/i915/gt/intel_engine_types.h | 4 ++-- > > 2 files changed, 8 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c b/drivers/gpu/drm/i915/gem/i915_gem_busy.c > > index 3d4f5775a4ba..25235ef630c1 100644 > > --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c > > +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c > > @@ -9,16 +9,16 @@ > > #include "i915_gem_ioctls.h" > > #include "i915_gem_object.h" > > > > -static __always_inline u32 __busy_read_flag(u8 id) > > +static __always_inline u32 __busy_read_flag(u16 id) > > { > > - if (id == (u8)I915_ENGINE_CLASS_INVALID) > > + if (id == (u16)I915_ENGINE_CLASS_INVALID) > > return 0xffff0000u; > > > > GEM_BUG_ON(id >= 16); > > return 0x10000u << id; > > } > > > > -static __always_inline u32 __busy_write_id(u8 id) > > +static __always_inline u32 __busy_write_id(u16 id) > > { > > /* > > * The uABI guarantees an active writer is also amongst the read > > @@ -29,14 +29,14 @@ static __always_inline u32 __busy_write_id(u8 id) > > * last_read - hence we always set both read and write busy for > > * last_write. > > */ > > - if (id == (u8)I915_ENGINE_CLASS_INVALID) > > + if (id == (u16)I915_ENGINE_CLASS_INVALID) > > return 0xffffffffu; > > > > return (id + 1) | __busy_read_flag(id); > > } > > > > static __always_inline unsigned int > > -__busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u8 id)) > > +__busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u16 id)) > > { > > const struct i915_request *rq; > > > > @@ -57,7 +57,7 @@ __busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u8 id)) > > return 0; > > > > /* Beware type-expansion follies! */ > > - BUILD_BUG_ON(!typecheck(u8, rq->engine->uabi_class)); > > + BUILD_BUG_ON(!typecheck(u16, rq->engine->uabi_class)); > > return flag(rq->engine->uabi_class); > > } > > > > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h > > index 00287515e7af..350da59e605b 100644 > > --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h > > +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h > > @@ -278,8 +278,8 @@ struct intel_engine_cs { > > u8 class; > > u8 instance; > > > > - u8 uabi_class; > > - u8 uabi_instance; > > + u16 uabi_class; > > + u16 uabi_instance; Bah, doesn't this leave us with a u16 hole! -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx