linux-kernel - Re: PANIC: double fault, error_code: 0x0 in 4.0.0-rc3-2, kvm related?

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Message-ID: <s5hiodxjnqs.wl-tiwai@suse.de>
Date:	Thu, 19 Mar 2015 11:16:43 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Stefan Seyfried <stefan.seyfried@...glemail.com>,
	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>
Subject: Re: PANIC: double fault, error_code: 0x0 in 4.0.0-rc3-2, kvm related?

Hi,

sorry to take time to back to this topic.

At Wed, 18 Mar 2015 15:29:14 -0700,
Andy Lutomirski wrote:
> 
> On Wed, Mar 18, 2015 at 3:22 PM, Jiri Kosina <jkosina@...e.cz> wrote:
> > On Wed, 18 Mar 2015, Andy Lutomirski wrote:
> >
> >> sysret64 can only fail with #GP, and we're totally screwed if that
> >> happens,
> >
> > But what if the GPF handler pagefaults afterwards? It'd be operating on
> > user stack already.
> 
> Good point.
> 
> Stefan, can you try changing the first "jne
> opportunistic_sysret_failed" to "jmp opportunistic_sysret_failed" in
> entry_64.S and seeing if you can reproduce this?  (Is it easy enough
> to reproduce that this would tell us anything?)

I tried this, and the same crash still happens.

On my machine (a Dell desktop with IvyBridge 4-core, 8GB RAM), I could
reproduce it relatively easily.  Start a desktop session as usual, and
start a KVM with 1GB memory 4 CPU, and start compiling a kernel on VM
with make -j4.  Meanwhile, start compiling a kernel with make -j8 on
the host, too.  So nothing too special there.  The kconfig is attached
below.

Currently I haven't set up kdump for this machine due to the disk
space.  Will try to adjust somehow from now on.

Takashi

Download attachment ".config" of type "application/octet-stream" (109087 bytes)