From patchwork Mon Aug 2 15:48:03 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 12414323 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=-18.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 4D359C4320E for ; Mon, 2 Aug 2021 15:49:01 +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 1961D60F50 for ; Mon, 2 Aug 2021 15:49:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 1961D60F50 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 72F186E598; Mon, 2 Aug 2021 15:48:46 +0000 (UTC) Received: from mail-ed1-x531.google.com (mail-ed1-x531.google.com [IPv6:2a00:1450:4864:20::531]) by gabe.freedesktop.org (Postfix) with ESMTPS id 5B3ED6E52A for ; Mon, 2 Aug 2021 15:48:44 +0000 (UTC) Received: by mail-ed1-x531.google.com with SMTP id z11so2678963edb.11 for ; Mon, 02 Aug 2021 08:48:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=0I2iZJJoQsIF6yXqV+vejJebZ5/RnHWA0EHrV1Aavnc=; b=ZXqYA/utyFMnEg94V4m/ZX+pdp4YMmLOi4ZR/WE55b8IAxHcCnGnOz7eQHi4JL2xlx l9SQU2iQF0xep+DMwa3xN2cGJjaWHrqTUcYHCkwjY02mPjFqJdjfm9i7jvd1XhMTcKAG ZtHMIFQuVGHVngo8Dwn1G6FI+oq3DmeHtr8aM= 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=0I2iZJJoQsIF6yXqV+vejJebZ5/RnHWA0EHrV1Aavnc=; b=WjCDOCJAlSEZBS/wErESspkx6VyHlkObTVsvUkY4RhzfJnbDdyd1EcNTU5rxM2uKTS zxP4JWla47QoK0Su4PdgjppNNyRK4mfaNGSEtWVb+G8c38p5nvqqL2m010X1PbbzotJJ MxSbOtuL7h95o/gaA+96YRQQRqEq7mHpt7sKxWy2t2OirthQJ79MNEanFgJS9JZVnTR5 pqqPvVJ32ZCj5+5XpjHzAXJooYGn5sQqFqzXY3XIw0WeTGTuWv5LCiDVkwsuqO8tRMnf YhgD5PGRy6PLFolujZswXUiqIu51eN4qlRI6h+9fYywkEkm/pPJgx2IJbIdOK6XPm6/B m5zQ== X-Gm-Message-State: AOAM533kf4ZYBHx+D1NuIHgVadKMKW900IoOLMYYVy8wcW5K3T21EWdj ITFV6Ip5yo5qObtX+l+vezAQIR/u6Yah2A== X-Google-Smtp-Source: ABdhPJzhfNw5GJ9LeteZgpg65RFnRChN3yEs4xmO99xwNaDfNtFJIozdvBwfa87oPYnzENCDIFyw0Q== X-Received: by 2002:aa7:c357:: with SMTP id j23mr5473762edr.370.1627919322955; Mon, 02 Aug 2021 08:48:42 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id m20sm5064020edv.67.2021.08.02.08.48.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Aug 2021 08:48:42 -0700 (PDT) From: Daniel Vetter To: DRI Development Cc: Intel Graphics Development , Daniel Vetter , Daniel Vetter , Jon Bloomfield , Chris Wilson , Maarten Lankhorst , Joonas Lahtinen , =?utf-8?q?Thomas_Hellstr?= =?utf-8?q?=C3=B6m?= , Matthew Auld , Lionel Landwerlin , Dave Airlie , Jason Ekstrand Subject: [PATCH 6/9] drm/i915: Drop __rcu from gem_context->vm Date: Mon, 2 Aug 2021 17:48:03 +0200 Message-Id: <20210802154806.3710472-7-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210802154806.3710472-1-daniel.vetter@ffwll.ch> References: <20210802154806.3710472-1-daniel.vetter@ffwll.ch> 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: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" It's been invariant since commit ccbc1b97948ab671335e950271e39766729736c3 Author: Jason Ekstrand Date: Thu Jul 8 10:48:30 2021 -0500 drm/i915/gem: Don't allow changing the VM on running contexts (v4) this just completes the deed. I've tried to split out prep work for more careful review as much as possible, this is what's left: - get_ppgtt gets simplified since we don't need to grab a temporary reference - we can rely on the temporary reference for the gem_ctx while we inspect the vm. The new vm_id still needs a full i915_vm_open ofc. This also removes the final caller of context_get_vm_rcu - A pile of selftests can now just look at ctx->vm instead of rcu_dereference_protected( , true) or similar things. - All callers of i915_gem_context_vm also disappear. - I've changed the hugepage selftest to set scrub_64K without any locking, because when we inspect that setting we're also not taking any locks either. It works because it's a selftests that's careful (single threaded gives you nice ordering) and not a live driver where races can happen from anywhere. These can only be split up further if we have some intermediate state with a bunch more rcu_dereference_protected(ctx->vm, true), just to shut up lockdep and sparse. The conversion to __rcu happened in commit a4e7ccdac38ec8335d9e4e2656c1a041c77feae1 Author: Chris Wilson Date: Fri Oct 4 14:40:09 2019 +0100 drm/i915: Move context management under GEM Note that we're not breaking the actual bugfix in there: The real bugfix is pushing the i915_vm_relase onto a separate worker, to avoid locking inversion issues. The rcu conversion was just thrown in for entertainment value on top (no vm lookup isn't even close to anything that's a hotpath where removing the single spinlock can be measured). Signed-off-by: Daniel Vetter Cc: Jon Bloomfield Cc: Chris Wilson Cc: Maarten Lankhorst Cc: Joonas Lahtinen Cc: Daniel Vetter Cc: "Thomas Hellström" Cc: Matthew Auld Cc: Lionel Landwerlin Cc: Dave Airlie Cc: Jason Ekstrand Reported-by: kernel test robot --- drivers/gpu/drm/i915/gem/i915_gem_context.c | 53 ++----------------- drivers/gpu/drm/i915/gem/i915_gem_context.h | 14 ++--- .../gpu/drm/i915/gem/i915_gem_context_types.h | 2 +- .../gpu/drm/i915/gem/selftests/huge_pages.c | 4 +- .../drm/i915/gem/selftests/i915_gem_context.c | 24 ++++----- drivers/gpu/drm/i915/i915_trace.h | 2 +- drivers/gpu/drm/i915/selftests/i915_vma.c | 2 +- 7 files changed, 21 insertions(+), 80 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c index fd24a1236682..2f3cc73d4710 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c @@ -735,44 +735,6 @@ static int set_proto_ctx_param(struct drm_i915_file_private *fpriv, return ret; } -static struct i915_address_space * -context_get_vm_rcu(struct i915_gem_context *ctx) -{ - GEM_BUG_ON(!rcu_access_pointer(ctx->vm)); - - do { - struct i915_address_space *vm; - - /* - * We do not allow downgrading from full-ppgtt [to a shared - * global gtt], so ctx->vm cannot become NULL. - */ - vm = rcu_dereference(ctx->vm); - if (!kref_get_unless_zero(&vm->ref)) - continue; - - /* - * This ppgtt may have be reallocated between - * the read and the kref, and reassigned to a third - * context. In order to avoid inadvertent sharing - * of this ppgtt with that third context (and not - * src), we have to confirm that we have the same - * ppgtt after passing through the strong memory - * barrier implied by a successful - * kref_get_unless_zero(). - * - * Once we have acquired the current ppgtt of ctx, - * we no longer care if it is released from ctx, as - * it cannot be reallocated elsewhere. - */ - - if (vm == rcu_access_pointer(ctx->vm)) - return rcu_pointer_handoff(vm); - - i915_vm_put(vm); - } while (1); -} - static int intel_context_set_gem(struct intel_context *ce, struct i915_gem_context *ctx, struct intel_sseu sseu) @@ -1193,7 +1155,7 @@ static void context_close(struct i915_gem_context *ctx) set_closed_name(ctx); - vm = i915_gem_context_vm(ctx); + vm = ctx->vm; if (vm) i915_vm_close(vm); @@ -1350,7 +1312,7 @@ i915_gem_create_context(struct drm_i915_private *i915, vm = &ppgtt->vm; } if (vm) { - RCU_INIT_POINTER(ctx->vm, i915_vm_open(vm)); + ctx->vm = i915_vm_open(vm); /* i915_vm_open() takes a reference */ i915_vm_put(vm); @@ -1576,15 +1538,12 @@ static int get_ppgtt(struct drm_i915_file_private *file_priv, if (!i915_gem_context_is_full_ppgtt(ctx)) return -ENODEV; - rcu_read_lock(); - vm = context_get_vm_rcu(ctx); - rcu_read_unlock(); - if (!vm) - return -ENODEV; + vm = ctx->vm; + GEM_BUG_ON(!vm); err = xa_alloc(&file_priv->vm_xa, &id, vm, xa_limit_32b, GFP_KERNEL); if (err) - goto err_put; + return err; i915_vm_open(vm); @@ -1592,8 +1551,6 @@ static int get_ppgtt(struct drm_i915_file_private *file_priv, args->value = id; args->size = 0; -err_put: - i915_vm_put(vm); return err; } diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.h b/drivers/gpu/drm/i915/gem/i915_gem_context.h index 37536a260e6e..7696bc91647d 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.h @@ -148,17 +148,11 @@ static inline void i915_gem_context_put(struct i915_gem_context *ctx) kref_put(&ctx->ref, i915_gem_context_release); } -static inline struct i915_address_space * -i915_gem_context_vm(struct i915_gem_context *ctx) -{ - return rcu_dereference_protected(ctx->vm, lockdep_is_held(&ctx->mutex)); -} - static inline bool i915_gem_context_is_full_ppgtt(struct i915_gem_context *ctx) { - GEM_BUG_ON(!!rcu_access_pointer(ctx->vm) != HAS_FULL_PPGTT(ctx->i915)); + GEM_BUG_ON(!!ctx->vm != HAS_FULL_PPGTT(ctx->i915)); - return !!rcu_access_pointer(ctx->vm); + return !!ctx->vm; } static inline struct i915_address_space * @@ -166,12 +160,10 @@ i915_gem_context_get_eb_vm(struct i915_gem_context *ctx) { struct i915_address_space *vm; - rcu_read_lock(); - vm = rcu_dereference(ctx->vm); + vm = ctx->vm; if (!vm) vm = &ctx->i915->ggtt.vm; vm = i915_vm_get(vm); - rcu_read_unlock(); return vm; } 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 94c03a97cb77..540ad16204a9 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h @@ -262,7 +262,7 @@ struct i915_gem_context { * In other modes, this is a NULL pointer with the expectation that * the caller uses the shared global GTT. */ - struct i915_address_space __rcu *vm; + struct i915_address_space *vm; /** * @pid: process id of creator diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c index 6c68fe26bb32..5d71626a1ee5 100644 --- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c +++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c @@ -1688,11 +1688,9 @@ int i915_gem_huge_page_live_selftests(struct drm_i915_private *i915) goto out_file; } - mutex_lock(&ctx->mutex); - vm = i915_gem_context_vm(ctx); + vm = ctx->vm; if (vm) WRITE_ONCE(vm->scrub_64K, true); - mutex_unlock(&ctx->mutex); err = i915_subtests(tests, ctx); diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c index 5442b8e59629..49d17701d8d3 100644 --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c @@ -27,12 +27,6 @@ #define DW_PER_PAGE (PAGE_SIZE / sizeof(u32)) -static inline struct i915_address_space *ctx_vm(struct i915_gem_context *ctx) -{ - /* single threaded, private ctx */ - return rcu_dereference_protected(ctx->vm, true); -} - static int live_nop_switch(void *arg) { const unsigned int nctx = 1024; @@ -813,7 +807,7 @@ static int igt_shared_ctx_exec(void *arg) struct i915_gem_context *ctx; struct intel_context *ce; - ctx = kernel_context(i915, ctx_vm(parent)); + ctx = kernel_context(i915, parent->vm); if (IS_ERR(ctx)) { err = PTR_ERR(ctx); goto out_test; @@ -823,7 +817,7 @@ static int igt_shared_ctx_exec(void *arg) GEM_BUG_ON(IS_ERR(ce)); if (!obj) { - obj = create_test_object(ctx_vm(parent), + obj = create_test_object(parent->vm, file, &objects); if (IS_ERR(obj)) { err = PTR_ERR(obj); @@ -1380,7 +1374,7 @@ static int igt_ctx_readonly(void *arg) goto out_file; } - vm = ctx_vm(ctx) ?: &i915->ggtt.alias->vm; + vm = ctx->vm ?: &i915->ggtt.alias->vm; if (!vm || !vm->has_read_only) { err = 0; goto out_file; @@ -1499,7 +1493,7 @@ static int write_to_scratch(struct i915_gem_context *ctx, GEM_BUG_ON(offset < I915_GTT_PAGE_SIZE); - err = check_scratch(ctx_vm(ctx), offset); + err = check_scratch(ctx->vm, offset); if (err) return err; @@ -1596,7 +1590,7 @@ static int read_from_scratch(struct i915_gem_context *ctx, GEM_BUG_ON(offset < I915_GTT_PAGE_SIZE); - err = check_scratch(ctx_vm(ctx), offset); + err = check_scratch(ctx->vm, offset); if (err) return err; @@ -1739,7 +1733,7 @@ static int check_scratch_page(struct i915_gem_context *ctx, u32 *out) u32 *vaddr; int err = 0; - vm = ctx_vm(ctx); + vm = ctx->vm; if (!vm) return -ENODEV; @@ -1801,7 +1795,7 @@ static int igt_vm_isolation(void *arg) } /* We can only test vm isolation, if the vm are distinct */ - if (ctx_vm(ctx_a) == ctx_vm(ctx_b)) + if (ctx_a->vm == ctx_b->vm) goto out_file; /* Read the initial state of the scratch page */ @@ -1813,8 +1807,8 @@ static int igt_vm_isolation(void *arg) if (err) goto out_file; - vm_total = ctx_vm(ctx_a)->total; - GEM_BUG_ON(ctx_vm(ctx_b)->total != vm_total); + vm_total = ctx_a->vm->total; + GEM_BUG_ON(ctx_b->vm->total != vm_total); count = 0; num_engines = 0; diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h index 806ad688274b..237e5061381b 100644 --- a/drivers/gpu/drm/i915/i915_trace.h +++ b/drivers/gpu/drm/i915/i915_trace.h @@ -1246,7 +1246,7 @@ DECLARE_EVENT_CLASS(i915_context, TP_fast_assign( __entry->dev = ctx->i915->drm.primary->index; __entry->ctx = ctx; - __entry->vm = rcu_access_pointer(ctx->vm); + __entry->vm = ctx->vm; ), TP_printk("dev=%u, ctx=%p, ctx_vm=%p", diff --git a/drivers/gpu/drm/i915/selftests/i915_vma.c b/drivers/gpu/drm/i915/selftests/i915_vma.c index 79ba72da0813..1f10fe36619b 100644 --- a/drivers/gpu/drm/i915/selftests/i915_vma.c +++ b/drivers/gpu/drm/i915/selftests/i915_vma.c @@ -39,7 +39,7 @@ static bool assert_vma(struct i915_vma *vma, { bool ok = true; - if (vma->vm != rcu_access_pointer(ctx->vm)) { + if (vma->vm != ctx->vm) { pr_err("VMA created with wrong VM\n"); ok = false; }