From patchwork Thu May 27 16:26:28 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jason Ekstrand X-Patchwork-Id: 12284777 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=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 DA252C47089 for ; Thu, 27 May 2021 16:27:29 +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 A7A3261074 for ; Thu, 27 May 2021 16:27:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A7A3261074 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 8C4E46F454; Thu, 27 May 2021 16:27:23 +0000 (UTC) Received: from mail-pf1-x434.google.com (mail-pf1-x434.google.com [IPv6:2607:f8b0:4864:20::434]) by gabe.freedesktop.org (Postfix) with ESMTPS id 5D52D6F446 for ; Thu, 27 May 2021 16:27:06 +0000 (UTC) Received: by mail-pf1-x434.google.com with SMTP id f22so1016539pfn.0 for ; Thu, 27 May 2021 09:27:06 -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=0VxWhnGfWOs2hBO/r4l2YJZlznPOWb2MIS5HjJWcTJA=; b=Z1s0AC/lzrkpRvaKxo3lkITA0SfEJdG+4ZLY846sbJ11JGLKvC0YeNMZGqng5DbLET jXCu3vzqCvfwD52TwzvjRr2vp2mGkstXlveOMW42LzycEuwwFaYybNc0RyCPjBtp4ean jePnzG8lyIE3WpQqSjQTNqLprn25oVY2Fq3h/tEhi2uElYsPxSkeFCqtnzNExb8HiFRw S/4NoKn287E7tIB5MvS6ti3eyx19aCBVqKJuGhBUZQKDTysjuncPD9oyz9DQGc/0aV4G IhRiIP8KqEZDWcBWeVm+Rsj1V/YPXkq+wS3rEc1DoJJ43Zsr/vZd8Kl39TDpqqLpFi2w chaQ== 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=0VxWhnGfWOs2hBO/r4l2YJZlznPOWb2MIS5HjJWcTJA=; b=hz824H0EBUC2Bigz1cdPcX4cqGr9X+lVHGCCBiLt+E66Tg4Cxc6BExytwKZJRa3aKE h5pN3N4pPikMZveKDm1jzbA6ZdjiOVCQ82nM+6QoeaC3EJ7iCtDl3a19sdLdpsQp91Zb AQyw9ezTBU3B1rYgezy/exOjlxMsZWz9c+xuv2IDNO+mJMB4JVQDavjF6VyZxNsLdJjU oLvOFMDioL+Axe9md039rg4IdqYenMdWrKU6FWopFa7oORd2VzqKHK6WqQ6fkLNHfkyP C2bLpi9wCuSw6YBcFoW1Ta5kQ2/rFRqPvx4tv07A+pf1yVTT6mBJwqe1W1KXgdmR+JXR 4KvA== X-Gm-Message-State: AOAM530k1vGXIHFsnTFXS6t0tlk7YynX0EOahjjC/9oo51zqVK16wvZ8 VUDb5o2YeE7FkXlZgyXE31u/JA== X-Google-Smtp-Source: ABdhPJx3T9vO1KLDoNk5r4zFiqMPwTJ4XO3vjRzBtfWac5Y+dPf8gRpFPsHD4hPLuvy6NwxxnW0iDQ== X-Received: by 2002:a63:e642:: with SMTP id p2mr4315518pgj.316.1622132825849; Thu, 27 May 2021 09:27:05 -0700 (PDT) Received: from omlet.com ([134.134.139.83]) by smtp.gmail.com with ESMTPSA id h9sm2298711pja.42.2021.05.27.09.27.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 May 2021 09:27:05 -0700 (PDT) From: Jason Ekstrand To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: [PATCH 07/29] drm/i915: Implement SINGLE_TIMELINE with a syncobj (v4) Date: Thu, 27 May 2021 11:26:28 -0500 Message-Id: <20210527162650.1182544-8-jason@jlekstrand.net> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210527162650.1182544-1-jason@jlekstrand.net> References: <20210527162650.1182544-1-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: Daniel Vetter , 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 Reviewed-by: Daniel Vetter --- 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 97613e529aab3..aa792c9517e16 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: