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

[Takashi Iwai]

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@xxxxxxx> 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

Attachment: .config
Description: Binary data