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From: "Noralf Trønnes" <noralf@tronnes.org>
To: "Ahmed S. Darwish" <darwish.07@gmail.com>,
	"David Airlie" <airlied@linux.ie>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Jani Nikula" <jani.nikula@linux.intel.com>,
	"Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>,
	"Rodrigo Vivi" <rodrigo.vivi@intel.com>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Christian König" <christian.koenig@amd.com>,
	"David Zhou" <David1.Zhou@amd.com>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"Matt Fleming" <matt@codeblueprint.co.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	dri-devel@lists.freedesktop.org,
	John Ogness <john.ogness@linutronix.de>,
	linux-kernel@vger.kernel.org
Subject: Re: DRM-based Oops viewer
Date: Mon, 11 Mar 2019 18:47:36 +0100
Message-ID: <ae91e388-3fcd-19e7-3a83-9279f294ffd5@tronnes.org> (raw)
In-Reply-To: <20190310013142.GA3376@darwi-home-pc>



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
> 

      parent reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-10  1:31 Ahmed S. Darwish
2019-03-10  8:44 ` Martin Steigerwald
2019-03-11  9:04 ` Jani Nikula
2019-03-11 13:49   ` Daniel Vetter
2019-03-11 23:39     ` Ahmed S. Darwish
2019-03-11 22:12   ` Ahmed S. Darwish
2019-03-12 10:20     ` Jani Nikula
2019-03-11 12:10 ` Joonas Lahtinen
2019-03-11 17:47 ` Noralf Trønnes [this message]

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