From patchwork Thu Apr 29 19:03:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jason Ekstrand X-Patchwork-Id: 12231701 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=-16.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 2E1F6C43460 for ; Thu, 29 Apr 2021 19:04:10 +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 E0F636143E for ; Thu, 29 Apr 2021 19:04:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E0F636143E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=jlekstrand.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 66D4F6F459; Thu, 29 Apr 2021 19:03:58 +0000 (UTC) Received: from mail-pj1-x102b.google.com (mail-pj1-x102b.google.com [IPv6:2607:f8b0:4864:20::102b]) by gabe.freedesktop.org (Postfix) with ESMTPS id 986886F459 for ; Thu, 29 Apr 2021 19:03:57 +0000 (UTC) Received: by mail-pj1-x102b.google.com with SMTP id y22-20020a17090a8b16b0290150ae1a6d2bso437815pjn.0 for ; Thu, 29 Apr 2021 12:03:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=jlekstrand-net.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=/suOcRFw1vdHRsSXXeAie2peFRiISvO2NIBvU7QrSRk=; b=LG8ipYtzixE4p/WRJOux6wBtOHj1foqHlN/rZVzQHbczusFA5f5fOi2rv1idmxdasA HqDV6GhgQliSz0f+GGLljwWXyr4LjTymaJ8+C4CVNW5Q3WueEFSwegKZeLEngIK3byCF 6bmMFV/AyoV+wxcMAg3THNFAT1TbIjOtm2ntBEPfmFfK3hDhiBdYdbL8JofKWDmthFP/ EfK7M7zI4iU666+JY4xRP//8cGZJqOnz9MHF3fkqPzLPIyOtaQ/VvmSH5mB/311/Tmb/ T6k6wvwG7VuOEyMH7uf5G7OXhMjV/uSav5QYK9U1Zwv8jNWTdhM5uc2EN9ioiZrKSGhl t6iw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=/suOcRFw1vdHRsSXXeAie2peFRiISvO2NIBvU7QrSRk=; b=mKHvuNOOuGoxE2xXPNVgesjHJHVBDIj6aGaOiQZNyIwpuypsLB7Sr11o48CjQAiuw5 la1XcSL0ctWAdkZxItUPBeFhpt0mv6xnXW4eGWaSdsQM108YJ6l8973K/TxJ+tlpjyoH k4inhnvE2IGPWKm5ZeSpwQRjSxrudw3cwHo06GqgRFzkG781zbYufJ6AYW4RZYDuBegn UaQ5DsSqVpEolPWceAiPuVKu93qDGPW6hHvpofBrBdn11yiH4O8hzCKHupRA6MhiwGJu mPOAi156RGZtYHE4ECVDklWwIiA/ZB1y9R/OwPhNDm0eKTcgHikJZfP4p9lEcsVOcvAz jKOQ== X-Gm-Message-State: AOAM5300wiQ732HhhLYwgwkTbfnENT3Cz4gw8hIAvvGcLhRkNzLO6II5 NK0Lv8rsvCPDMETCXaPURkLo7Q== X-Google-Smtp-Source: ABdhPJyFU16824KQ9x+HAwGCE5Uv2Ye3KTZX5NU3DTncrmLb77UWBAjwOoEgJARj7AFQIWmRsaVecQ== X-Received: by 2002:a17:902:ea03:b029:ec:fddc:c529 with SMTP id s3-20020a170902ea03b02900ecfddcc529mr1120147plg.83.1619723037063; Thu, 29 Apr 2021 12:03:57 -0700 (PDT) Received: from omlet.lan ([134.134.139.83]) by smtp.gmail.com with ESMTPSA id b21sm3114405pji.39.2021.04.29.12.03.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Apr 2021 12:03:56 -0700 (PDT) From: Jason Ekstrand To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: [PATCH 07/25] drm/i915: Implement SINGLE_TIMELINE with a syncobj (v4) Date: Thu, 29 Apr 2021 14:03:22 -0500 Message-Id: <20210429190340.1555632-8-jason@jlekstrand.net> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210429190340.1555632-1-jason@jlekstrand.net> References: <20210429190340.1555632-1-jason@jlekstrand.net> MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Matthew Brost , Jason Ekstrand Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" This API is entirely unnecessary and I'd love to get rid of it. If userspace wants a single timeline across multiple contexts, they can either use implicit synchronization or a syncobj, both of which existed at the time this feature landed. The justification given at the time was that it would help GL drivers which are inherently single-timeline. However, neither of our GL drivers actually wanted the feature. i965 was already in maintenance mode at the time and iris uses syncobj for everything. Unfortunately, as much as I'd love to get rid of it, it is used by the media driver so we can't do that. We can, however, do the next-best thing which is to embed a syncobj in the context and do exactly what we'd expect from userspace internally. This isn't an entirely identical implementation because it's no longer atomic if userspace races with itself by calling execbuffer2 twice simultaneously from different threads. It won't crash in that case; it just doesn't guarantee any ordering between those two submits. It also means that sync files exported from different engines on a SINGLE_TIMELINE context will have different fence contexts. This is visible to userspace if it looks at the obj_name field of sync_fence_info. Moving SINGLE_TIMELINE to a syncobj emulation has a couple of technical advantages beyond mere annoyance. One is that intel_timeline is no longer an api-visible object and can remain entirely an implementation detail. This may be advantageous as we make scheduler changes going forward. Second is that, together with deleting the CLONE_CONTEXT API, we should now have a 1:1 mapping between intel_context and intel_timeline which may help us reduce locking. v2 (Tvrtko Ursulin): - Update the comment on i915_gem_context::syncobj to mention that it's an emulation and the possible race if userspace calls execbuffer2 twice on the same context concurrently. v2 (Jason Ekstrand): - Wrap the checks for eb.gem_context->syncobj in unlikely() - Drop the dma_fence reference - Improved commit message v3 (Jason Ekstrand): - Move the dma_fence_put() to before the error exit v4 (Tvrtko Ursulin): - Add a comment about fence contexts to the commit message Signed-off-by: Jason Ekstrand Cc: Maarten Lankhorst Cc: Matthew Brost --- drivers/gpu/drm/i915/gem/i915_gem_context.c | 49 +++++-------------- .../gpu/drm/i915/gem/i915_gem_context_types.h | 14 +++++- .../gpu/drm/i915/gem/i915_gem_execbuffer.c | 16 ++++++ 3 files changed, 40 insertions(+), 39 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c index 308a63f778faf..3f99ef5a72f57 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c @@ -67,6 +67,8 @@ #include #include +#include + #include "gt/gen6_ppgtt.h" #include "gt/intel_context.h" #include "gt/intel_context_param.h" @@ -224,10 +226,6 @@ static void intel_context_set_gem(struct intel_context *ce, ce->vm = vm; } - GEM_BUG_ON(ce->timeline); - if (ctx->timeline) - ce->timeline = intel_timeline_get(ctx->timeline); - if (ctx->sched.priority >= I915_PRIORITY_NORMAL && intel_engine_has_timeslices(ce->engine)) __set_bit(CONTEXT_USE_SEMAPHORES, &ce->flags); @@ -351,9 +349,6 @@ void i915_gem_context_release(struct kref *ref) mutex_destroy(&ctx->engines_mutex); mutex_destroy(&ctx->lut_mutex); - if (ctx->timeline) - intel_timeline_put(ctx->timeline); - put_pid(ctx->pid); mutex_destroy(&ctx->mutex); @@ -570,6 +565,9 @@ static void context_close(struct i915_gem_context *ctx) if (vm) i915_vm_close(vm); + if (ctx->syncobj) + drm_syncobj_put(ctx->syncobj); + ctx->file_priv = ERR_PTR(-EBADF); /* @@ -765,33 +763,11 @@ static void __assign_ppgtt(struct i915_gem_context *ctx, i915_vm_close(vm); } -static void __set_timeline(struct intel_timeline **dst, - struct intel_timeline *src) -{ - struct intel_timeline *old = *dst; - - *dst = src ? intel_timeline_get(src) : NULL; - - if (old) - intel_timeline_put(old); -} - -static void __apply_timeline(struct intel_context *ce, void *timeline) -{ - __set_timeline(&ce->timeline, timeline); -} - -static void __assign_timeline(struct i915_gem_context *ctx, - struct intel_timeline *timeline) -{ - __set_timeline(&ctx->timeline, timeline); - context_apply_all(ctx, __apply_timeline, timeline); -} - static struct i915_gem_context * i915_gem_create_context(struct drm_i915_private *i915, unsigned int flags) { struct i915_gem_context *ctx; + int ret; if (flags & I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE && !HAS_EXECLISTS(i915)) @@ -820,16 +796,13 @@ i915_gem_create_context(struct drm_i915_private *i915, unsigned int flags) } if (flags & I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE) { - struct intel_timeline *timeline; - - timeline = intel_timeline_create(&i915->gt); - if (IS_ERR(timeline)) { + ret = drm_syncobj_create(&ctx->syncobj, + DRM_SYNCOBJ_CREATE_SIGNALED, + NULL); + if (ret) { context_close(ctx); - return ERR_CAST(timeline); + return ERR_PTR(ret); } - - __assign_timeline(ctx, timeline); - intel_timeline_put(timeline); } trace_i915_context_create(ctx); diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h index 676592e27e7d2..df76767f0c41b 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h @@ -83,7 +83,19 @@ struct i915_gem_context { struct i915_gem_engines __rcu *engines; struct mutex engines_mutex; /* guards writes to engines */ - struct intel_timeline *timeline; + /** + * @syncobj: Shared timeline syncobj + * + * When the SHARED_TIMELINE flag is set on context creation, we + * emulate a single timeline across all engines using this syncobj. + * For every execbuffer2 call, this syncobj is used as both an in- + * and out-fence. Unlike the real intel_timeline, this doesn't + * provide perfect atomic in-order guarantees if the client races + * with itself by calling execbuffer2 twice concurrently. However, + * if userspace races with itself, that's not likely to yield well- + * defined results anyway so we choose to not care. + */ + struct drm_syncobj *syncobj; /** * @vm: unique address space (GTT) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c index b812f313422a9..d640bba6ad9ab 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c @@ -3460,6 +3460,16 @@ i915_gem_do_execbuffer(struct drm_device *dev, goto err_vma; } + if (unlikely(eb.gem_context->syncobj)) { + struct dma_fence *fence; + + fence = drm_syncobj_fence_get(eb.gem_context->syncobj); + err = i915_request_await_dma_fence(eb.request, fence); + dma_fence_put(fence); + if (err) + goto err_ext; + } + if (in_fence) { if (args->flags & I915_EXEC_FENCE_SUBMIT) err = i915_request_await_execution(eb.request, @@ -3517,6 +3527,12 @@ i915_gem_do_execbuffer(struct drm_device *dev, fput(out_fence->file); } } + + if (unlikely(eb.gem_context->syncobj)) { + drm_syncobj_replace_fence(eb.gem_context->syncobj, + &eb.request->fence); + } + i915_request_put(eb.request); err_vma: