From patchwork Fri Apr 23 22:31:16 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jason Ekstrand X-Patchwork-Id: 12221859 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 02B3BC433ED for ; Fri, 23 Apr 2021 22:32:01 +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 BB48F6113D for ; Fri, 23 Apr 2021 22:32:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB48F6113D 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 13E366ECB2; Fri, 23 Apr 2021 22:31:50 +0000 (UTC) Received: from mail-pf1-x42c.google.com (mail-pf1-x42c.google.com [IPv6:2607:f8b0:4864:20::42c]) by gabe.freedesktop.org (Postfix) with ESMTPS id D78ED6ECAB for ; Fri, 23 Apr 2021 22:31:46 +0000 (UTC) Received: by mail-pf1-x42c.google.com with SMTP id m11so34975775pfc.11 for ; Fri, 23 Apr 2021 15:31:46 -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=/i3TjgiFgKtmiEefAjw6hXE7Lu1ZwY2eDE/tGEb2mto=; b=AA1Lx2E/T6KOo8sOgbP8i0JGCp/Dc4hJ1vQzqfWykmwaRXGRdaVy7/f/SojXXaqxPW QhHC0k2gk52rkASCM+o3Upmrwyq30Ogt8pXQQ9NJWsU3YWcBV9LjwfUhbfhcCRk+Cyg3 VWC74ZvD1OaSFav5ZS7/LoeVr83Ch38BscwHO3bJk8lLGt+taWGRT5DgwI4UJiYO9VJe rS/oFCcTQcs9d/NdSXwxy2/2oCRdPWlKBFr+YklTNtWCK0zAs1Axie3aCUyJCNJhn5nf DfQoPuiox3pwuQT5S+fHlnLWLUu7NFeipmqo1u4S0NNidqcUB6kqjo+mheZ2bsKyalXk 7L1A== 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=/i3TjgiFgKtmiEefAjw6hXE7Lu1ZwY2eDE/tGEb2mto=; b=Bs6hkNgjATFan/OHPCJb68XPhDOL//K3LMALUq0kV4KNoEldflME01vRp1k3R6wHL0 GzvaSy6tiVyDa9rqo0ug8yK5KA+BiN20YldeuURI9HKqSmFjrACqPwFyjze4nj+3fIoW NsVsHlqzMyFjTYjgPjdXe7RRfTKx5Xnpo4oefhIAy8n+0QRiXJLftSyxnGYElH48U9id /FWc3G6aSm+0wouyc+hti3O5KbGlX63yyDYD74cK6DCzHvbhj8UkMBpiM1rP1ZuROxGw ZOL6Gk4iQzQdq9c2Tc/lJkmXZyObMdauUQM94FLW0R0kC6mZaGRdYTCht90/she5rd/v +wcg== X-Gm-Message-State: AOAM530CnZ8S5GbarRDelRMSAGuMo0oK2woWkVOKUgQxrNRqWG2LgECJ OpKrvdK8FuRYP6evWH2V7m7yZw== X-Google-Smtp-Source: ABdhPJyDPgDJ9YEuRWicffRG+3vfUGB8ukgFUPTDHb5oN/6L3BAMwOcEEyy8AtLKm4Ten+V0BwAsdw== X-Received: by 2002:a63:4a1a:: with SMTP id x26mr5912198pga.429.1619217106342; Fri, 23 Apr 2021 15:31:46 -0700 (PDT) Received: from omlet.com ([134.134.139.76]) by smtp.gmail.com with ESMTPSA id z12sm5523420pfn.195.2021.04.23.15.31.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Apr 2021 15:31:45 -0700 (PDT) From: Jason Ekstrand To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: [PATCH 06/21] drm/i915: Implement SINGLE_TIMELINE with a syncobj (v3) Date: Fri, 23 Apr 2021 17:31:16 -0500 Message-Id: <20210423223131.879208-7-jason@jlekstrand.net> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210423223131.879208-1-jason@jlekstrand.net> References: <20210423223131.879208-1-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. 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 (Jason Ekstrand): - 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. - 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 Signed-off-by: Jason Ekstrand Cc: Maarten Lankhorst Cc: Matthew Brost 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 2c2fefa912805..a72c9b256723b 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" @@ -225,10 +227,6 @@ 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: