linux-kernel - Re: [PATCH] x86, kdump, ioapic: Fix kdump race with migrating irq

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120131222751.GE5650@redhat.com>
Date:	Tue, 31 Jan 2012 17:27:51 -0500
From:	Don Zickus <dzickus@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
	vgoyal@...hat.com, kexec-list <kexec@...ts.infradead.org>
Subject: Re: [PATCH] x86, kdump, ioapic: Fix kdump race with migrating irq

On Tue, Jan 31, 2012 at 02:08:29PM -0800, Eric W. Biederman wrote:
> > The problem is that although kdump tries to shutdown minimal hardware,
> > it still needs to disable the IO APIC.  This requires spinlocks which
> > may be held by another cpu.  This other cpu is being held infinitely in
> > an NMI context by kdump in order to serialize the crashing path.  Instant
> > deadlock.
> 
> Can you test to see if kexec on panic still needs to disable the IO
> APIC.  Last I looked we were close if not all of the way there to not
> needing to boot the kernel in pic mode?

Ok, so you just blindly remove disable_IO_APIC from
native_machine_crash_shutdown and re-run some panic tests on various
machines?  What about the disable_IO_APIC path in native_machine_shutdown?

Also, where could I look to see if that work was done?  Is that in the
ioapic setup code?

> 
> If we can skip the ioapic disable entirely we should be much more
> robust.

Agreed.

Cheers,
Don
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/