From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D68BEB64D7 for ; Mon, 26 Jun 2023 21:32:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230078AbjFZVcP (ORCPT ); Mon, 26 Jun 2023 17:32:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34154 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230093AbjFZVcM (ORCPT ); Mon, 26 Jun 2023 17:32:12 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4758E10C9 for ; Mon, 26 Jun 2023 14:32:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Sender:Reply-To:Content-ID:Content-Description; bh=3WrV9FP4eW8Nnv/icMs114y+kK2oX4SvQP8ltNtE+5I=; b=yF8txQHE+JLtPnr/RSwcuSzZnC eEnAsz4U2YWpunoAyK5pJqyyG+WYpfWuzHhaZZ/HKebLX/nJ1xK05v6lfOlGYLswflyZaHsRUolmP wql48+oGq7ToJMBoMgTEIwX1kBxZrDghYRVTOrZHlH2WLlHDOdvmjShNJJ43wDhY+oNve91leQ+KB pdOw5mlN4+vZ36YmcH5OaiFNQnQWPJN7n8xN8iW+wH8tlKeqWsv6wVmiD0WlU3T9c/GswVXU6GBH2 cFG5NrdEEUh/7EdqClshXDWBeSJTrkFbw1z0/jYAyG4oJnu9POSKDOlQAspBYmx+eQ1iqda1eCUoq SNd2Am7g==; Received: from [2601:1c2:980:9ec0::2764] by bombadil.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1qDtoY-00B4pY-2A; Mon, 26 Jun 2023 21:32:02 +0000 Message-ID: Date: Mon, 26 Jun 2023 14:32:00 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.2 Subject: Re: [PATCH v4 1/1] drm/doc: Document DRM device reset expectations Content-Language: en-US To: =?UTF-8?Q?Andr=c3=a9_Almeida?= , dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: kernel-dev@igalia.com, alexander.deucher@amd.com, christian.koenig@amd.com, pierre-eric.pelloux-prayer@amd.com, Simon Ser , Rob Clark , Pekka Paalanen , Daniel Vetter , Daniel Stone , =?UTF-8?B?J01hcmVrIE9sxaHDoWsn?= , Dave Airlie , =?UTF-8?Q?Michel_D=c3=a4nzer?= , Samuel Pitoiset , =?UTF-8?Q?Timur_Krist=c3=b3f?= , Bas Nieuwenhuizen References: <20230626183347.55118-1-andrealmeid@igalia.com> <20230626183347.55118-2-andrealmeid@igalia.com> From: Randy Dunlap In-Reply-To: <20230626183347.55118-2-andrealmeid@igalia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 6/26/23 11:33, André Almeida wrote: > Create a section that specifies how to deal with DRM device resets for > kernel and userspace drivers. > > Signed-off-by: André Almeida > --- > Documentation/gpu/drm-uapi.rst | 68 ++++++++++++++++++++++++++++++++++ > 1 file changed, 68 insertions(+) > > diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst > index 65fb3036a580..25a11b9b98fa 100644 > --- a/Documentation/gpu/drm-uapi.rst > +++ b/Documentation/gpu/drm-uapi.rst > @@ -285,6 +285,74 @@ for GPU1 and GPU2 from different vendors, and a third handler for > mmapped regular files. Threads cause additional pain with signal > handling as well. > > +Device reset > +============ > + > +The GPU stack is really complex and is prone to errors, from hardware bugs, > +faulty applications and everything in between the many layers. Some errors > +require resetting the device in order to make the device usable again. This > +section describes what is the expectations for DRM and usermode drivers when a sections describes the expectations for DRM and usermode drivers when a > +device resets and how to propagate the reset status. > + > +Kernel Mode Driver > +------------------ > + > +The KMD is responsible for checking if the device needs a reset, and to perform > +it as needed. Usually a hang is detected when a job gets stuck executing. KMD > +should keep track of resets, because userspace can query any time about the > +reset stats for an specific context. This is needed to propagate to the rest of > +the stack that a reset has happened. Currently, this is implemented by each > +driver separately, with no common DRM interface. > + > +User Mode Driver > +---------------- > + > +The UMD should check before submitting new commands to the KMD if the device has > +been reset, and this can be checked more often if it requires to. After more often if the UMD requires it. After > +detecting a reset, UMD will then proceed to report it to the application using > +the appropriated API error code, as explained in the below section about appropriate the section below about > +robustness. > + > +Robustness > +---------- > + > +The only way to try to keep an application working after a reset is if it > +complies with the robustness aspects of the graphical API that it is using. > + > +Graphical APIs provide ways to application to deal with device resets. However, to applications > +there is no guarantee that the app will be correctly using such features, and will use such features correctly, and a // or "and the" > +UMD can implement policies to close the app if it is a repeating offender, > +likely in a broken loop. This is done to ensure that it does not keeps blocking keep > +the user interface from being correctly displayed. This should be done even if > +the app is correct but happens to trigger some bug in the hardware/driver. > + > +OpenGL > +~~~~~~ > + > +Apps using OpenGL should use the available robust interfaces, like the > +extension ``GL_ARB_robustness`` (or ``GL_EXT_robustness`` for OpenGL ES). This > +interface tells if a reset has happened, and if so, all the context state is > +considered lost and the app proceeds by creating new ones. If is possible to If it is possible to > +determine that robustness is not in use, UMD will terminate the app when a reset the UMD > +is detected, giving that the contexts are lost and the app won't be able to > +figure this out and recreate the contexts. > + > +Vulkan > +~~~~~~ > + > +Apps using Vulkan should check for ``VK_ERROR_DEVICE_LOST`` for submissions. > +This error code means, among other things, that a device reset has happened and > +it needs to recreate the contexts to keep going. > + > +Reporting resets causes That's an awkward heading. How about: Reporting causes of resets -------------------------- > +----------------------- > + > +Apart from propagating the reset through the stack so apps can recover, it's > +really useful for driver developers to learn more about what caused the reset in > +first place. DRM devices should make use of devcoredump to store relevant > +information about the reset, so this information can be added to user bug > +reports. > + > .. _drm_driver_ioctl: > > IOCTL Support on Device Nodes thanks for the documentation. -- ~Randy