From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C9B9034A3DB; Wed, 20 May 2026 06:51:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.112 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779259887; cv=pass; b=KmhxE1ePyvpY5TykJEo9EpAJM+RhkMWlbrbIi5tj1A/Gy3DN9zbKJEKRnUUIrTFT808bSnn+mZbAX3Slkkl0riK9FdOrktv3jKoowQvBP50sbzYVE8WRa0Ifc6J0VV5OLnTSr9Ikds+Lt4Oxh0bGY0H9Q8ldA5tCzOIPRER0LHU= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779259887; c=relaxed/simple; bh=hjmjJgRAJge/Gcp0b3nocweBDpeY80SE4udUFeY0rfU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=isExqzsOUKRjqNYurqcLP9cXPaPpE325VTYrYGrYb4iEh+6uYI/kua1CE1NkNcNdhldHAt9AZPEm6HgVHDS03yI7oVC4OXKWQO89+s+2zRyrNetw1jPi+7Vztbb6k4YSbMthClVZxw8d45xPKc2p6BZ6BwWIj0FJlEl+C/lqhCA= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (1024-bit key) header.d=collabora.com header.i=dmitry.osipenko@collabora.com header.b=VyBRdddL; arc=pass smtp.client-ip=136.143.188.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=collabora.com header.i=dmitry.osipenko@collabora.com header.b="VyBRdddL" ARC-Seal: i=1; a=rsa-sha256; t=1779259867; cv=none; d=zohomail.com; s=zohoarc; b=KLBTvPulm89Uhd0hrY1hQxXpIYJTSoEldAsWjb56Om/sPBEyUexkg5UYpxkjSIk1Tx3YG4JCbfdh8YTIPVlDM648iQOWxDquMJesPQzQ1s7tWNmdTKndnH3qvAMDXU7EGxZBtv7NsMBN23KUsSXVwWwQ0guDs+qdzXfxl33EynE= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1779259867; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=QB0aBnlsYuDj3KTGtL3n3HDsaBFK9L6LJNUmMJHUjY4=; b=TQ4oJAJ5bv64cMiBCvxeYed1fC9/kbkPzdecrFlE/ugUI2IfR8DX8iWgrLWnKVSKl4dr7qwDZfIZnvn7uZtrrqmJ2VX12BDTTIxworgPS5sKSNt3gB/zsyJ0J4OBDGDUqHiIz4ne1ULiW8oWwJbNqpky+i4eJTHT/vpTs56Uu8A= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=dmitry.osipenko@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1779259867; s=zohomail; d=collabora.com; i=dmitry.osipenko@collabora.com; h=Message-ID:Date:Date:MIME-Version:Subject:Subject:To:To:Cc:Cc:References:From:From:In-Reply-To:Content-Type:Content-Transfer-Encoding:Message-Id:Reply-To; bh=QB0aBnlsYuDj3KTGtL3n3HDsaBFK9L6LJNUmMJHUjY4=; b=VyBRdddLQLmNW2QZQ1V6CEYZt7nEdTgavdMYB1VurOPR3uoTzn/Njegc8oYzgnEi mtKQuEWzIzHS0ewTEdnXWjWXclzSQloH9N7gOvvhx4GhpUqSfJd8GKNonSYeD/ppXd3 6mN7WVM9Azu9aLYjLp/XnYTR32QL+/zIiNg2Xbmg= Received: by mx.zohomail.com with SMTPS id 1779259866052944.3067294851667; Tue, 19 May 2026 23:51:06 -0700 (PDT) Message-ID: Date: Wed, 20 May 2026 09:50:54 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] drm/virtio: use uninterruptible resv lock for plane updates To: =?UTF-8?Q?Christian_K=C3=B6nig?= , Deepanshu Kartikey , airlied@redhat.com, kraxel@redhat.com, gurchetansingh@chromium.org, olvaffe@gmail.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, simona@ffwll.ch, sumit.semwal@linaro.org Cc: dri-devel@lists.freedesktop.org, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, syzbot+72bd3dd3a5d5f39a0271@syzkaller.appspotmail.com, stable@vger.kernel.org References: <20260519082247.34470-1-kartikey406@gmail.com> <2e23513c-9d59-4891-acfe-9f1fbcbce778@amd.com> Content-Language: en-US From: Dmitry Osipenko In-Reply-To: <2e23513c-9d59-4891-acfe-9f1fbcbce778@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ZohoMailClient: External On 5/19/26 11:27, Christian König wrote: > On 5/19/26 10:22, Deepanshu Kartikey wrote: >> virtio_gpu_cursor_plane_update() and virtio_gpu_resource_flush() lock >> the framebuffer BO's dma_resv via virtio_gpu_array_lock_resv() and >> ignore its return value. The function can fail with -EINTR from >> dma_resv_lock_interruptible() (signal during lock wait) or with >> -ENOMEM from dma_resv_reserve_fences() (fence slot allocation), >> leaving the resv lock not held. The queue path then walks the object >> array and calls dma_resv_add_fence(), which requires the lock held; >> with lockdep enabled this trips dma_resv_assert_held(): >> >> WARNING: drivers/dma-buf/dma-resv.c:296 at dma_resv_add_fence+0x71e/0x840 >> Call Trace: >> virtio_gpu_array_add_fence >> virtio_gpu_queue_ctrl_sgs >> virtio_gpu_queue_fenced_ctrl_buffer >> virtio_gpu_cursor_plane_update >> drm_atomic_helper_commit_planes >> drm_atomic_helper_commit_tail >> commit_tail >> drm_atomic_helper_commit >> drm_atomic_commit >> drm_atomic_helper_update_plane >> __setplane_atomic >> drm_mode_cursor_universal >> drm_mode_cursor_common >> drm_mode_cursor_ioctl >> drm_ioctl >> __x64_sys_ioctl >> >> Beyond the WARN, mutating the dma_resv fence list without the lock >> races with concurrent readers/writers and can corrupt the list. > > Well why are you trying to add a fence on an atomic mode set in the first place? > > That is usually an illegal operation here. That is pre-existing in the driver. It performs draw operation and in some cases waits for the completion during atomic. Whether all that syncing is correct is hard to say immediately as some of it may be historical edge cases. -- Best regards, Dmitry