Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751692AbdILRyt (ORCPT ); Tue, 12 Sep 2017 13:54:49 -0400 Received: from mail-wr0-f196.google.com ([209.85.128.196]:33189 "EHLO mail-wr0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751493AbdILRys (ORCPT ); Tue, 12 Sep 2017 13:54:48 -0400 X-Google-Smtp-Source: ADKCNb6a+QBvonufUmw0N1twpfXD4zr3M7o67M/Q3GcCQGB30qNRbA0c2HuUl5QKPYq9W9H2AwIh+IhvG3HxwkRNVqI= MIME-Version: 1.0 In-Reply-To: References: <20170912173530.14132-1-colin.king@canonical.com> <211c7afe-c778-cf39-760a-05bc3a62e5db@vmware.com> From: Emil Velikov Date: Tue, 12 Sep 2017 18:54:45 +0100 Message-ID: Subject: Re: [PATCH] drm/vmwgfx: remove DRM_ERROR message, stops log spamming To: Colin Ian King Cc: Thomas Hellstrom , VMware Graphics , Sinclair Yeh , David Airlie , ML dri-devel , kernel-janitors@vger.kernel.org, "Linux-Kernel@Vger. Kernel. Org" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1481 Lines: 35 On 12 September 2017 at 18:47, Colin Ian King wrote: > On 12/09/17 18:42, Thomas Hellstrom wrote: >> Hi, Colin, >> >> On 09/12/2017 07:35 PM, Colin King wrote: >>> From: Colin Ian King >>> >>> mmap'ing the device multiple times will spam the kernel log with the >>> DRM_ERROR message about illegal mmap'ing the old fifo space. >> How are you hitting this? Multiple mappings should be fine as long as >> mapping offsets are correct, >> so hitting this message should indicate that the user-space app is doing >> something seriously wrong, and >> having it present in the log should probably help more than it hurts. >> >> /Thomas > > Good question. I hit similar issues with the drm qxl driver when > running some kernel regression tests with stress-ng [1]. I realize this > is an artificial test scenario so it is definitely not a typical > use-case, however, sync the illegal mmapping will return -EINVAL the > application will pick up that this is an error without the need of > spotting it in the kernel log. And a user space application can perform > many millions of these invalid mmaps causing kernel log spamming. > FWIW I'm the one to "blame" here - pointing Colin to drop the message. Two reasons come to mind: - there is a unwritten rule that roughly says "user input should not cause kernel log spam" - out of all the DRM drivers only QXL and VMWGFX print a message, with a patch addressing the former HTH Emil