From patchwork Sat Jul 9 08:38:51 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 958942 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) by demeter2.kernel.org (8.14.4/8.14.4) with ESMTP id p698eY2E013904 for ; Sat, 9 Jul 2011 08:40:54 GMT Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id CC3D59ED43 for ; Sat, 9 Jul 2011 01:40:33 -0700 (PDT) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from fireflyinternet.com (server109-228-6-236.live-servers.net [109.228.6.236]) by gabe.freedesktop.org (Postfix) with ESMTP id 457FBA08A9 for ; Sat, 9 Jul 2011 01:38:56 -0700 (PDT) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.66.37; Received: from arrandale.alporthouse.com (unverified [78.156.66.37]) by fireflyinternet.com (Firefly Internet SMTP) with ESMTP id 39130551-1500050 for multiple; Sat, 09 Jul 2011 09:38:53 +0100 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Sat, 9 Jul 2011 09:38:51 +0100 Message-Id: <1310200731-18086-2-git-send-email-chris@chris-wilson.co.uk> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1310200731-18086-1-git-send-email-chris@chris-wilson.co.uk> References: <1310200731-18086-1-git-send-email-chris@chris-wilson.co.uk> X-Originating-IP: 78.156.66.37 Subject: [Intel-gfx] [PATCH 2/2] drm/i915: Disable page-faults around the fast pwrite/pread paths X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.11 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: intel-gfx-bounces+patchwork-intel-gfx=patchwork.kernel.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+patchwork-intel-gfx=patchwork.kernel.org@lists.freedesktop.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter2.kernel.org [140.211.167.43]); Sat, 09 Jul 2011 08:40:54 +0000 (UTC) These paths hold onto the struct mutex whilst accessing pages. In order, to prevent a recursive dead-lock should we fault-in a GTT mapped page we need to return -EFAULT and fallback to the slow path. Lockdep has complained before about the potential dead-lock, but rvis is the first application found to sufficiently abuse the API to trigger it. Cursory performance regression testing on a 1GiB PineView system using x11perf, cairo-perf-trace, glxgears and a few game benchmarks suggested no large regressions with just a 2% slowdown for firefox. The caveat is that this was an otherwise idle system and that for 32-bit systems io_mapping_map_atomic_wc() already disabled page-faults. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38115 Signed-off-by: Chris Wilson --- drivers/gpu/drm/i915/i915_gem.c | 22 ++++++++++++++++++++-- 1 files changed, 20 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 2fce620..ecb27fd 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -365,9 +365,15 @@ i915_gem_shmem_pread_fast(struct drm_device *dev, return PTR_ERR(page); vaddr = kmap_atomic(page); + /* We have to disable faulting here in case the user address + * is really a GTT mapping and so we can not enter + * i915_gem_fault() whilst already holding struct_mutex. + */ + pagefault_disable(); ret = __copy_to_user_inatomic(user_data, vaddr + page_offset, page_length); + pagefault_enable(); kunmap_atomic(vaddr); mark_page_accessed(page); @@ -593,8 +599,14 @@ fast_user_write(struct io_mapping *mapping, unsigned long unwritten; vaddr_atomic = io_mapping_map_atomic_wc(mapping, page_base); + /* We have to disable faulting here in case the user address + * is really a GTT mapping and so we can not enter + * i915_gem_fault() whilst already holding struct_mutex. + */ + pagefault_disable(); unwritten = __copy_from_user_inatomic_nocache(vaddr_atomic + page_offset, user_data, length); + pagefault_enable(); io_mapping_unmap_atomic(vaddr_atomic); return unwritten; } @@ -812,11 +824,17 @@ i915_gem_shmem_pwrite_fast(struct drm_device *dev, if (IS_ERR(page)) return PTR_ERR(page); - vaddr = kmap_atomic(page, KM_USER0); + vaddr = kmap_atomic(page); + /* We have to disable faulting here in case the user address + * is really a GTT mapping and so we can not enter + * i915_gem_fault() whilst already holding struct_mutex. + */ + pagefault_disable(); ret = __copy_from_user_inatomic(vaddr + page_offset, user_data, page_length); - kunmap_atomic(vaddr, KM_USER0); + pagefault_enable(); + kunmap_atomic(vaddr); set_page_dirty(page); mark_page_accessed(page);