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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable 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 F2AFBC433DF for ; Tue, 9 Jun 2020 15:15:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D837D2074B for ; Tue, 9 Jun 2020 15:15:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730569AbgFIPPk convert rfc822-to-8bit (ORCPT ); Tue, 9 Jun 2020 11:15:40 -0400 Received: from mail.fireflyinternet.com ([109.228.58.192]:49771 "EHLO fireflyinternet.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730436AbgFIPPk (ORCPT ); Tue, 9 Jun 2020 11:15:40 -0400 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 21444154-1500050 for multiple; Tue, 09 Jun 2020 16:15:29 +0100 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT In-Reply-To: <20200609122856.10207-1-chris@chris-wilson.co.uk> References: <20200609122856.10207-1-chris@chris-wilson.co.uk> Cc: Mika Kuoppala , stable@vger.kernel.org To: intel-gfx@lists.freedesktop.org Subject: Re: [PATCH] drm/i915/gt: Incrementally check for rewinding From: Chris Wilson Message-ID: <159171572885.24308.5160778009299838490@build.alporthouse.com> User-Agent: alot/0.8.1 Date: Tue, 09 Jun 2020 16:15:28 +0100 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Quoting Chris Wilson (2020-06-09 13:28:56) > In commit 5ba32c7be81e ("drm/i915/execlists: Always force a context > reload when rewinding RING_TAIL"), we placed the check for rewinding a > context on actually submitting the next request in that context. This > was so that we only had to check once, and could do so with precision > avoiding as many forced restores as possible. For example, to ensure > that we can resubmit the same request a couple of times, we include a > small wa_tail such that on the next submission, the ring->tail will > appear to move forwards when resubmitting the same request. This is very > common as it will happen for every lite-restore to fill the second port > after a context switch. > > However, intel_ring_direction() is limited in precision to movements of > upto half the ring size. The consequence being that if we tried to > unwind many requests, we could exceed half the ring and flip the sense > of the direction, so missing a force restore. As no request can be > greater than half the ring (i.e. 2048 bytes in the smallest case), we > can check for rollback incrementally. As we check against the tail that > would be submitted, we do not lose any sensitivity and allow lite > restores for the simple case. We still need to double check upon > submitting the context, to allow for multiple preemptions and > resubmissions. > > Fixes: 5ba32c7be81e ("drm/i915/execlists: Always force a context reload when rewinding RING_TAIL") > Signed-off-by: Chris Wilson > Cc: Mika Kuoppala > Cc: # v5.4+ > --- > drivers/gpu/drm/i915/gt/intel_engine_cs.c | 4 +- > drivers/gpu/drm/i915/gt/intel_lrc.c | 21 +++- > drivers/gpu/drm/i915/gt/intel_ring.c | 4 + > drivers/gpu/drm/i915/gt/selftest_mocs.c | 18 ++- > drivers/gpu/drm/i915/gt/selftest_ring.c | 110 ++++++++++++++++++ > .../drm/i915/selftests/i915_mock_selftests.h | 1 + > 6 files changed, 154 insertions(+), 4 deletions(-) > create mode 100644 drivers/gpu/drm/i915/gt/selftest_ring.c > > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c > index e5141a897786..0a05301e00fb 100644 > --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c > +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c > @@ -646,7 +646,7 @@ static int engine_setup_common(struct intel_engine_cs *engine) > struct measure_breadcrumb { > struct i915_request rq; > struct intel_ring ring; > - u32 cs[1024]; > + u32 cs[2048]; > }; > > static int measure_breadcrumb_dw(struct intel_context *ce) > @@ -667,6 +667,8 @@ static int measure_breadcrumb_dw(struct intel_context *ce) > > frame->ring.vaddr = frame->cs; > frame->ring.size = sizeof(frame->cs); > + frame->ring.wrap = > + BITS_PER_TYPE(frame->ring.size) - ilog2(frame->ring.size); > frame->ring.effective_size = frame->ring.size; > intel_ring_update_space(&frame->ring); > frame->rq.ring = &frame->ring; > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c > index a057f7a2a521..f66274e60bb6 100644 > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c > @@ -1137,6 +1137,13 @@ __unwind_incomplete_requests(struct intel_engine_cs *engine) > list_move(&rq->sched.link, pl); > set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags); > > + /* Check for rollback incrementally */ > + if (intel_ring_direction(rq->ring, > + intel_ring_wrap(rq->ring, > + rq->tail), > + rq->ring->tail) <= 0) > + rq->context->lrc.desc |= CTX_DESC_FORCE_RESTORE; We could be a bit more cheeky in that the problem only occurs if we rollback far enough that there is a danger is mistaking the rollback for a forward update. -Chris 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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 7608AC433DF for ; Tue, 9 Jun 2020 15:15:36 +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 46EB02074B for ; Tue, 9 Jun 2020 15:15:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 46EB02074B 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 F176D6E123; Tue, 9 Jun 2020 15:15:35 +0000 (UTC) Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id 358286E123 for ; Tue, 9 Jun 2020 15:15:34 +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 21444154-1500050 for multiple; Tue, 09 Jun 2020 16:15:29 +0100 MIME-Version: 1.0 In-Reply-To: <20200609122856.10207-1-chris@chris-wilson.co.uk> References: <20200609122856.10207-1-chris@chris-wilson.co.uk> To: intel-gfx@lists.freedesktop.org From: Chris Wilson Message-ID: <159171572885.24308.5160778009299838490@build.alporthouse.com> User-Agent: alot/0.8.1 Date: Tue, 09 Jun 2020 16:15:28 +0100 Subject: Re: [Intel-gfx] [PATCH] drm/i915/gt: Incrementally check for rewinding 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: , Cc: stable@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Quoting Chris Wilson (2020-06-09 13:28:56) > In commit 5ba32c7be81e ("drm/i915/execlists: Always force a context > reload when rewinding RING_TAIL"), we placed the check for rewinding a > context on actually submitting the next request in that context. This > was so that we only had to check once, and could do so with precision > avoiding as many forced restores as possible. For example, to ensure > that we can resubmit the same request a couple of times, we include a > small wa_tail such that on the next submission, the ring->tail will > appear to move forwards when resubmitting the same request. This is very > common as it will happen for every lite-restore to fill the second port > after a context switch. > > However, intel_ring_direction() is limited in precision to movements of > upto half the ring size. The consequence being that if we tried to > unwind many requests, we could exceed half the ring and flip the sense > of the direction, so missing a force restore. As no request can be > greater than half the ring (i.e. 2048 bytes in the smallest case), we > can check for rollback incrementally. As we check against the tail that > would be submitted, we do not lose any sensitivity and allow lite > restores for the simple case. We still need to double check upon > submitting the context, to allow for multiple preemptions and > resubmissions. > > Fixes: 5ba32c7be81e ("drm/i915/execlists: Always force a context reload when rewinding RING_TAIL") > Signed-off-by: Chris Wilson > Cc: Mika Kuoppala > Cc: # v5.4+ > --- > drivers/gpu/drm/i915/gt/intel_engine_cs.c | 4 +- > drivers/gpu/drm/i915/gt/intel_lrc.c | 21 +++- > drivers/gpu/drm/i915/gt/intel_ring.c | 4 + > drivers/gpu/drm/i915/gt/selftest_mocs.c | 18 ++- > drivers/gpu/drm/i915/gt/selftest_ring.c | 110 ++++++++++++++++++ > .../drm/i915/selftests/i915_mock_selftests.h | 1 + > 6 files changed, 154 insertions(+), 4 deletions(-) > create mode 100644 drivers/gpu/drm/i915/gt/selftest_ring.c > > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c > index e5141a897786..0a05301e00fb 100644 > --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c > +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c > @@ -646,7 +646,7 @@ static int engine_setup_common(struct intel_engine_cs *engine) > struct measure_breadcrumb { > struct i915_request rq; > struct intel_ring ring; > - u32 cs[1024]; > + u32 cs[2048]; > }; > > static int measure_breadcrumb_dw(struct intel_context *ce) > @@ -667,6 +667,8 @@ static int measure_breadcrumb_dw(struct intel_context *ce) > > frame->ring.vaddr = frame->cs; > frame->ring.size = sizeof(frame->cs); > + frame->ring.wrap = > + BITS_PER_TYPE(frame->ring.size) - ilog2(frame->ring.size); > frame->ring.effective_size = frame->ring.size; > intel_ring_update_space(&frame->ring); > frame->rq.ring = &frame->ring; > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c > index a057f7a2a521..f66274e60bb6 100644 > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c > @@ -1137,6 +1137,13 @@ __unwind_incomplete_requests(struct intel_engine_cs *engine) > list_move(&rq->sched.link, pl); > set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags); > > + /* Check for rollback incrementally */ > + if (intel_ring_direction(rq->ring, > + intel_ring_wrap(rq->ring, > + rq->tail), > + rq->ring->tail) <= 0) > + rq->context->lrc.desc |= CTX_DESC_FORCE_RESTORE; We could be a bit more cheeky in that the problem only occurs if we rollback far enough that there is a danger is mistaking the rollback for a forward update. -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx