From patchwork Thu Jun 24 07:04:57 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Brost X-Patchwork-Id: 12341119 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=-16.7 required=3.0 tests=BAYES_00, 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 6053CC49EA7 for ; Thu, 24 Jun 2021 06:49:00 +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 33495613CC for ; Thu, 24 Jun 2021 06:49:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 33495613CC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com 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 BD0406EA49; Thu, 24 Jun 2021 06:47:49 +0000 (UTC) Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by gabe.freedesktop.org (Postfix) with ESMTPS id DD3CA6E9F8; Thu, 24 Jun 2021 06:47:30 +0000 (UTC) IronPort-SDR: fuNdobdHUvZqPtDiNNU5NftieFkNrxWo2h1qAS+nzI6yaDk1ZXpdSMU3cvLUtQBIhQfuH9/caN Yr/+OQ13PBUA== X-IronPort-AV: E=McAfee;i="6200,9189,10024"; a="207346765" X-IronPort-AV: E=Sophos;i="5.83,295,1616482800"; d="scan'208";a="207346765" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jun 2021 23:47:26 -0700 IronPort-SDR: XKxJo6DUBcfP440MmCdVrRxR9sqet+PbTySLH0N1T7PyuzN5lXsASetYpOQC5d2/O9OhY9raAU mEZrLY9prQrw== X-IronPort-AV: E=Sophos;i="5.83,295,1616482800"; d="scan'208";a="556390948" Received: from dhiatt-server.jf.intel.com ([10.54.81.3]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jun 2021 23:47:25 -0700 From: Matthew Brost To: , Date: Thu, 24 Jun 2021 00:04:57 -0700 Message-Id: <20210624070516.21893-29-matthew.brost@intel.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20210624070516.21893-1-matthew.brost@intel.com> References: <20210624070516.21893-1-matthew.brost@intel.com> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH 28/47] drm/i915: Hold reference to intel_context over life of i915_request 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: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Hold a reference to the intel_context over life of an i915_request. Without this an i915_request can exist after the context has been destroyed (e.g. request retired, context closed, but user space holds a reference to the request from an out fence). In the case of GuC submission + virtual engine, the engine that the request references is also destroyed which can trigger bad pointer dref in fence ops (e.g. i915_fence_get_driver_name). We could likely change i915_fence_get_driver_name to avoid touching the engine but let's just be safe and hold the intel_context reference. Signed-off-by: Matthew Brost Reviewed-by: John Harrison --- drivers/gpu/drm/i915/i915_request.c | 54 ++++++++++++----------------- 1 file changed, 22 insertions(+), 32 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c index de9deb95b8b1..dec5a35c9aa2 100644 --- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -126,39 +126,17 @@ static void i915_fence_release(struct dma_fence *fence) i915_sw_fence_fini(&rq->semaphore); /* - * Keep one request on each engine for reserved use under mempressure - * - * We do not hold a reference to the engine here and so have to be - * very careful in what rq->engine we poke. The virtual engine is - * referenced via the rq->context and we released that ref during - * i915_request_retire(), ergo we must not dereference a virtual - * engine here. Not that we would want to, as the only consumer of - * the reserved engine->request_pool is the power management parking, - * which must-not-fail, and that is only run on the physical engines. - * - * Since the request must have been executed to be have completed, - * we know that it will have been processed by the HW and will - * not be unsubmitted again, so rq->engine and rq->execution_mask - * at this point is stable. rq->execution_mask will be a single - * bit if the last and _only_ engine it could execution on was a - * physical engine, if it's multiple bits then it started on and - * could still be on a virtual engine. Thus if the mask is not a - * power-of-two we assume that rq->engine may still be a virtual - * engine and so a dangling invalid pointer that we cannot dereference - * - * For example, consider the flow of a bonded request through a virtual - * engine. The request is created with a wide engine mask (all engines - * that we might execute on). On processing the bond, the request mask - * is reduced to one or more engines. If the request is subsequently - * bound to a single engine, it will then be constrained to only - * execute on that engine and never returned to the virtual engine - * after timeslicing away, see __unwind_incomplete_requests(). Thus we - * know that if the rq->execution_mask is a single bit, rq->engine - * can be a physical engine with the exact corresponding mask. + * Keep one request on each engine for reserved use under mempressure, + * do not use with virtual engines as this really is only needed for + * kernel contexts. */ - if (is_power_of_2(rq->execution_mask) && - !cmpxchg(&rq->engine->request_pool, NULL, rq)) + if (!intel_engine_is_virtual(rq->engine) && + !cmpxchg(&rq->engine->request_pool, NULL, rq)) { + intel_context_put(rq->context); return; + } + + intel_context_put(rq->context); kmem_cache_free(global.slab_requests, rq); } @@ -977,7 +955,18 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp) } } - rq->context = ce; + /* + * Hold a reference to the intel_context over life of an i915_request. + * Without this an i915_request can exist after the context has been + * destroyed (e.g. request retired, context closed, but user space holds + * a reference to the request from an out fence). In the case of GuC + * submission + virtual engine, the engine that the request references + * is also destroyed which can trigger bad pointer dref in fence ops + * (e.g. i915_fence_get_driver_name). We could likely change these + * functions to avoid touching the engine but let's just be safe and + * hold the intel_context reference. + */ + rq->context = intel_context_get(ce); rq->engine = ce->engine; rq->ring = ce->ring; rq->execution_mask = ce->engine->mask; @@ -1054,6 +1043,7 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp) GEM_BUG_ON(!list_empty(&rq->sched.waiters_list)); err_free: + intel_context_put(ce); kmem_cache_free(global.slab_requests, rq); err_unreserve: intel_context_unpin(ce);