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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81CE4C43381 for ; Mon, 11 Mar 2019 17:47:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 430902075C for ; Mon, 11 Mar 2019 17:47:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=tronnes.org header.i=@tronnes.org header.b="E8EvaWJr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727816AbfCKRrp (ORCPT ); Mon, 11 Mar 2019 13:47:45 -0400 Received: from smtp.domeneshop.no ([194.63.252.55]:55241 "EHLO smtp.domeneshop.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726641AbfCKRrp (ORCPT ); Mon, 11 Mar 2019 13:47:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=tronnes.org; s=ds201810; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=ur/8dlgtqOnLVlPjSbxLj+4bgqrBZNzB0TkHTqt8S4M=; b=E8EvaWJrIyajjnmiaBFfuwezWNIJMc0SVgFsqrPN9ZZYY54jfMcUGGCGQps+I4pukSEwcO6qrjBwaXyoBV8vtmBonW0g1FRuLxT45R+oOKb4senH4MP/z3yY8lJlfeL49SWlArNOrNMW2OAlf7TiL42AnIJAmKFMr8Ig6+zMVritiMgfxeffxdS3HtW788XaM86EENncvqQoFVYaClF+SoxzXhtaqO2gVKs8n6ZaelcJEsMTXjnWZ87W4tFuSGuNPNI053oQeEwtEwjeXdRCiFFYiQr7Eg3JF6Ud77ldTTHQofqSqEF/ymlZeXgg0xqwONRxQrDbr7XR/Dii2FOFpw==; Received: from 211.81-166-168.customer.lyse.net ([81.166.168.211]:50957 helo=[192.168.10.177]) by smtp.domeneshop.no with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.84_2) (envelope-from ) id 1h3P1Z-0000M3-Np; Mon, 11 Mar 2019 18:47:41 +0100 Subject: Re: DRM-based Oops viewer To: "Ahmed S. Darwish" , David Airlie , Daniel Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Alex Deucher , =?UTF-8?Q?Christian_K=c3=b6nig?= , David Zhou , Ard Biesheuvel , Matt Fleming Cc: Greg Kroah-Hartman , Linus Torvalds , dri-devel@lists.freedesktop.org, John Ogness , linux-kernel@vger.kernel.org References: <20190310013142.GA3376@darwi-home-pc> From: =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= Message-ID: Date: Mon, 11 Mar 2019 18:47:36 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.3 MIME-Version: 1.0 In-Reply-To: <20190310013142.GA3376@darwi-home-pc> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Den 10.03.2019 02.31, skrev Ahmed S. Darwish: > Hello DRM/UEFI maintainers, > > Several years ago, I wrote a set of patches to dump the kernel > log to disk upon panic -- through BIOS INT 0x13 services. [1] > > The overwhelming response was that it's unsafe to do this in a > generic manner. Linus proposed a video-based viewer instead: [2] > > If you want to do the BIOS services thing, do it for video: copy the > oops to low RAM, return to real mode, re-run the graphics card POST > routines to initialize text-mode, and use the BIOS to print out the > oops. That is WAY less scary than writing to disk. > > Of course it's 2019 now though, and it's quite known that > Intel is officially obsoleting the PC/AT BIOS by 2020.. [3] > > Researching whether this can be done from UEFI, it was also clear > that UEFI "Runtime Services" do not provide any re-initialization > routines. [4] > > The maximum possible that UEFI can provide is a GOP-provided > framebuffer that's ready to use by the OS -- even after the UEFI > boot phase is marked as done through ExitBootServices(). [5] > > Of course, once native drivers like i915 or radeon take over, > such a framebuffer is toast... [6] > > Thus a possible remaining option, is to display the oops through > "minimal" DRM drivers provided for each HW variant... Since > these special drivers will run only and fully under a panic() > context though, several constraints exist: > > - The code should be fully synchronous (irqs are disabled) > - It should not allocate any dynamic memory > - It should make minimal assumptions about HW state > - It should not chain into any other kernel subsystem > - It has ample freedom to use delay-based loops and the > like, the kernel is already dead. > > How feasible is it to have such a special "DRM viewoops" > framework + its minimal drivers in the kernel? > > The target is to start from i915, since that's what in my > laptop now, and work from there.. > > Some final notes: > > - The NT kernel has a similar concept, but for storage instead. > They're used to dump core under kernel panic() situations, > and are called "Minoport storage drivers". [7] > > - Since Windows 7+, a very fancy Blue Screen of Death is > displayed, with Unicode and whatnot, implying GPU drivers > involvement. [8] > > - Mac OS X also does something similar [9] > > - On Linux laptops, the current situation is _really_ bad. > > In any graphical session, type "echo c > /proc/sysrq-trigger"; > the screen will just completely freeze... > > Desired first goal: just print the panic() log > > Thanks a lot, > I just sent out a patchset I had lying around that tries to solve this: https://patchwork.freedesktop.org/series/57849/ Noralf. > [1] https://lore.kernel.org/lkml/20110125134748.GA10051@laptop > [2] https://lore.kernel.org/lkml/AANLkTinU0KYiCd4p=z+=ojbkeEoT2G+CAYvdRU02KJEn@mail.gmail.com > > [3] https://uefi.org/sites/default/files/resources/Brian_Richardson_Intel_Final.pdf > > [4] UEFI v2.7 spec, Chapter 8, "Services — Runtime Services" > [5] UEFI v2.7 spec, Section 12.9, "Graphics Output Protocol" > "The Graphics Output Protocol supports this capability by > providing the EFI OS loader access to a hardware frame buffer > and enough information to allow the OS to draw directly to > the graphics output device." > > [6] linux/drivers/gpu/drm/i915/i915_drv.c::i915_kick_out_firmware_fb() > linux/drivers/gpu/drm/radeon/radeon_drv.c::radeon_pci_probe() > > [7] https://docs.microsoft.com/en-us/windows-hardware/drivers/storage/restrictions-on-miniport-drivers-that-manage-the-boot-drive > > [8] https://upload.wikimedia.org/wikipedia/commons/archive/5/56/20181019151937%21Bsodwindows10.png > [9] https://upload.wikimedia.org/wikipedia/commons/4/4a/Mac_OS_X_10.2_Kernel_Panic.jpg > > --darwi > http://darwish.chasingpointers.com > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel >