From nobody Sun Sep 14 09:39:52 2025 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 B2447C05027 for ; Mon, 23 Jan 2023 20:27:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232356AbjAWU1v (ORCPT ); Mon, 23 Jan 2023 15:27:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58820 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232204AbjAWU1s (ORCPT ); Mon, 23 Jan 2023 15:27:48 -0500 Received: from fanzine2.igalia.com (fanzine2.igalia.com [213.97.179.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7FFDF210F for ; Mon, 23 Jan 2023 12:27:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:MIME-Version:References: In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=7CaXIdoI8n3ZxHPPdx/samyORw/Wg8sXLQapZ/RBkNE=; b=fCiKDcxtbjDgmimIhRvRxngTgb 85ecoNKuvlffUrBzca6OUqFTCOLG0GS7Y/xSl3W/9hbE+t0B2gyqmJSYiQuk2LBwWEegoZ3e1Beyv xgJQf92lfA0BDtJdh3VXEeAxhCTdb0SiB9pBHldjMxitNCo+e34ZQXEWuVcZ4CCgM4vOBcvQYSIhW biBOMXlXcpU/lrG4Mtc3zEEXRurpxjeAYqCxY5cs/Dp9scqHc3FsoQLXbr7lS2AIQfZTUxUN1f9wV qm1N6tVbRNqHdsnV/TnFYpgiZceWEIwPCtUflMN62LJnBvC709vFP0uHsyDCThSSeWu6mrVSc4kBS ACFvJknQ==; Received: from [177.102.82.39] (helo=steammachine.lan) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1pK3Pt-00GEfP-7R; Mon, 23 Jan 2023 21:27:45 +0100 From: =?UTF-8?q?Andr=C3=A9=20Almeida?= To: dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: kernel-dev@igalia.com, alexander.deucher@amd.com, contactshashanksharma@gmail.com, amaranath.somalapuram@amd.com, christian.koenig@amd.com, pierre-eric.pelloux-prayer@amd.com, Simon Ser , Rob Clark , Pekka Paalanen , Daniel Vetter , Daniel Stone , =?UTF-8?q?=27Marek=20Ol=C5=A1=C3=A1k=27?= , Dave Airlie , "Pierre-Loup A . Griffais" , =?UTF-8?q?Andr=C3=A9=20Almeida?= Subject: [RFC PATCH] drm: Create documentation about device resets Date: Mon, 23 Jan 2023 17:26:46 -0300 Message-Id: <20230123202646.356592-2-andrealmeid@igalia.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230123202646.356592-1-andrealmeid@igalia.com> References: <20230123202646.356592-1-andrealmeid@igalia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Create a document that specifies how to deal with DRM device resets for kernel and userspace drivers. Signed-off-by: Andr=C3=A9 Almeida --- Documentation/gpu/drm-reset.rst | 51 +++++++++++++++++++++++++++++++++ Documentation/gpu/index.rst | 1 + 2 files changed, 52 insertions(+) create mode 100644 Documentation/gpu/drm-reset.rst diff --git a/Documentation/gpu/drm-reset.rst b/Documentation/gpu/drm-reset.= rst new file mode 100644 index 000000000000..0dd11a469cf9 --- /dev/null +++ b/Documentation/gpu/drm-reset.rst @@ -0,0 +1,51 @@ +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +DRM Device Reset +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +The GPU stack is really complex and is prone to errors, from hardware bugs, +faulty applications and everything in the many layers in between. To recov= er +from this kind of state, sometimes is needed to reset the GPU. Unproper ha= ndling +of GPU resets can lead to an unstable userspace. This page describes what'= s the +expected behaviour from DRM drivers to do in those situations, from usermo= de +drivers and compositors as well. + +Robustness +---------- + +First of all, application robust APIs, when available, should be used. This +allows the application to correctly recover and continue to run after a re= set. +Apps that doesn't use this should be promptly killed when the kernel driver +detects that it's in broken state. Specifically guidelines for some APIs: + +- OpenGL: During a reset, KMD kill processes that haven't ARB Robustness + enabled, assuming they can't recover. +- Vulkan: Assumes that every app is able to deal with ``VK_ERROR_DEVICE_LO= ST``, + so KMD doesn't kill any. If it doesn't do it right, it's considered a br= oken + application and UMD will deal with it. + +Kernel mode driver +------------------ + +The KMD should be able to detect that something is wrong with the applicat= ion +and that a reset is needed to take place to recover the device (e.g. an en= dless +wait). It needs to properly track the context that is broken and mark it as +dead, so any other syscalls to that context should be further rejected. The +other contexts should be preserved when possible, avoid crashing the rest = of +userspace. KMD can ban a file descriptor that keeps causing resets, as it's +likely in a broken loop. + +User mode driver +---------------- + +During a reset, UMD should be aware that rejected syscalls indicates that = the +context is broken and for robust apps the recovery should happen for the +context. Non-robust apps would be already terminated by KMD. If no new con= text +is created for some time, it is assumed that the recovery didn't work, so = UMD +should terminate it. + +Compositors +----------- + +(In the long term) compositors should be robust as well to properly deal w= ith it +errors. Init systems should be aware of the compositor status and reset it= if is +broken. diff --git a/Documentation/gpu/index.rst b/Documentation/gpu/index.rst index b99dede9a5b1..300b2529bd39 100644 --- a/Documentation/gpu/index.rst +++ b/Documentation/gpu/index.rst @@ -9,6 +9,7 @@ Linux GPU Driver Developer's Guide drm-mm drm-kms drm-kms-helpers + drm-reset drm-uapi drm-usage-stats driver-uapi --=20 2.39.1