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From: Rusty Russell <rusty@rustcorp.com.au>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jeff Garzik" <jgarzik@pobox.com>,
	"Randy Dunlap" <rdunlap@xenotime.net>,
	"Mark Lord" <kernel@teksavvy.com>,
	"Ahmed S. Darwish" <darwish.07@gmail.com>,
	"James Bottomley" <James.Bottomley@suse.de>,
	"Tejun Heo" <tj@kernel.org>, "Ingo Molnar" <mingo@elte.hu>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>, X86-ML <x86@kernel.org>,
	"Tony Luck" <tony.luck@intel.com>,
	"Dave Jones" <davej@redhat.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Willy Tarreau" <wtarreau@hera.kernel.org>,
	"Willy Tarreau" <w@1wt.eu>,
	"Dirk Hohndel" <hohndel@infradead.org>,
	Dirk.Hohndel@intel.com, IDE-ML <linux-ide@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Peter Zijlstra" <a.p.zijlstra@chello.nl>,
	"Frédéric Weisbecker" <fweisbec@gmail.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Arjan van de Ven" <arjan@infradead.org>
Subject: Re: [PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk upon panic
Date: Mon, 31 Jan 2011 13:29:31 +1030	[thread overview]
Message-ID: <201101311329.31562.rusty@rustcorp.com.au> (raw)
In-Reply-To: <4D3F559C.1050809@zytor.com>

On Wed, 26 Jan 2011 09:28:36 am H. Peter Anvin wrote:
> On 01/25/2011 02:45 PM, Jeff Garzik wrote:
> > On 01/25/2011 05:16 PM, Randy Dunlap wrote:
> >> On Tue, 25 Jan 2011 17:10:49 -0500 Mark Lord wrote:
> >>
> >>> On 11-01-25 12:05 PM, Ahmed S. Darwish wrote:
> >>>>
> >>>> My current x86 laptop includes the very common ATA PIIX controller.
> >>>
> >>>
> >>> ata_piix is just about ideal for this sort of thing.
> >>>
> >>> Except, don't use the BIOS to write the logs,
> >>> but rather code/use a very simple set of polling-PIO
> >>> functions to talk directly through the PIIX to the drive.
> >>>
> >>> Really really simple code to do that, and it would likely
> >>> work with anything ata-piix, and most other non-AHCI chipsets too.
> >>>
> >>> Not perfect, but probably good enough for a lot of scenarios.
> >>> The old hd.c driver shows how to read/write a sector at a time,
> >>> and that kind of code is easily converted to simply poll for completion.
> >>
> >> I don't know how/where to find it, but Rusty Russell had a version of this
> >> many, many years ago.
> > 
> > You beat me to the reply :)
> > 
> > http://lwn.net/Articles/9905/
> > 
> > but IIRC there were updates and improvements.
> > 
> 
> "Not perfect" is really not good enough.  You're writing to the disk, so
> it *has* to be perfect.  That means dealing with having shared IDE/AHCI
> device and doing the right thing, and the possibility that the kernel
> has interrupts enabled, yadda yadda.

Not for the limited problem of trying to get some logs out.

My driver read the sectors, checked it was full of the magic signature, then
overwrote them.  It's possible for that to screw up, but unlikely.  The boot
script mailed it off to a central site, reset the sector and rearmed the
oopsdumper.

> In the end you end up with something that looks, again, like kexec/kdump.

That was the proposed solution back then, too.  If I'd realized how long
that would take to arrive, I would have kept pushing...

BTW, anyone know whether distros turn it on?    Ubuntu seems to enable it
in the config, but I've never seen it in action.  My laptop has frozen
a couple of times, but maybe it really froze...

Cheers,
Rusty.

  parent reply	other threads:[~2011-01-31  2:59 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-25 13:47 Ahmed S. Darwish
2011-01-25 13:51 ` [PATCH -next 1/2][RFC] x86: Saveoops: Switch to real-mode and call BIOS Ahmed S. Darwish
2011-01-25 17:26   ` H. Peter Anvin
2011-01-25 13:53 ` [PATCH -next 2/2][RFC] x86: Saveoops: Reserve low memory and register code Ahmed S. Darwish
2011-01-25 17:29   ` H. Peter Anvin
2011-01-26  9:04     ` Ahmed S. Darwish
2011-01-25 14:09 ` [PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk upon panic Ingo Molnar
2011-01-25 15:08   ` Tejun Heo
2011-01-25 17:33     ` H. Peter Anvin
2011-01-26 11:44       ` Ahmed S. Darwish
2011-02-03 14:36     ` Pavel Machek
2011-02-03 15:28       ` H. Peter Anvin
2011-02-03 17:57         ` Ingo Molnar
2011-02-03 21:07           ` H. Peter Anvin
2011-01-25 15:36   ` Ahmed S. Darwish
2011-01-25 16:02     ` James Bottomley
2011-01-25 17:05       ` Ahmed S. Darwish
2011-01-25 17:20         ` James Bottomley
2011-01-25 22:10         ` Mark Lord
2011-01-25 22:16           ` Randy Dunlap
2011-01-25 22:45             ` Jeff Garzik
2011-01-25 22:58               ` H. Peter Anvin
2011-01-26  0:26                 ` Jeff Garzik
2011-01-31  2:59                 ` Rusty Russell [this message]
2011-01-31 10:45                   ` Ingo Molnar
2011-01-25 17:32     ` Tony Luck
2011-01-25 17:36       ` H. Peter Anvin
2011-01-25 19:04       ` Jeff Garzik
2011-01-25 14:49 ` Tejun Heo
2011-01-28  7:59   ` Jan Ceuleers
2011-01-25 20:25 ` Linus Torvalds
     [not found]   ` <20110126124954.GC24527@laptop>
2011-01-26 23:07     ` Luck, Tony
     [not found]       ` <20110126231620.GA14807@redhat.com>
     [not found]         ` <987664A83D2D224EAE907B061CE93D53019438EB02@orsmsx505.amr.corp.intel.com>
     [not found]           ` <20110126233033.GB14807@redhat.com>
     [not found]             ` <987664A83D2D224EAE907B061CE93D53019438EBB6@orsmsx505.amr.corp.intel.com>
     [not found]               ` <4D40F7F1.3020509@zytor.com>
     [not found]                 ` <20110127120039.GD20279@elte.hu>
2011-01-27 18:35                   ` Luck, Tony
     [not found]                   ` <4D4197CB.9070201@zytor.com>
     [not found]                     ` <20110127162429.GB26437@elte.hu>
2011-01-27 18:56                       ` Luck, Tony
     [not found]     ` <20110127021338.GA20334@redhat.com>
     [not found]       ` <4D40F81E.1030009@zytor.com>
     [not found]         ` <20110127052639.GA16289@laptop>
     [not found]           ` <m1sjweyeax.fsf@fess.ebiederm.org>
2011-02-02 11:13             ` Ahmed S. Darwish

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