Re: Oops with tip/x86/fpu

Quentin Casasnovas
2015-03-05T08:37:21Z

On Wed, Mar 04, 2015 at 08:06:51PM +0100, Oleg Nesterov wrote:
> On 03/04, Dave Hansen wrote:
> >
> > I'm running a commit from the tip/x86/fpu branch: ae486033b98. It's on
> > a system which I normally boot with 'noxsaves'. When I boot without
> > 'noxsaves' it is getting a GPF around the time that init is forked off.
>
> And I assume that (before this commit) the kernel runs fine if you boot
> without 'noxsaves'?
>
> >
> > The full oops is below, but addr2line points to the "alternative_input("
> > line in xrstor_state().
> >
> > The one that oopses has this in bootup:
> >
> > xsave: enabled xstate_bv 0x1f, cntxt size 0x3c0 using compacted form
> >
> > The one that works says:
> >
> > xsave: enabled xstate_bv 0x1f, cntxt size 0x440 using standard form
> >
> Thanks. I'll try to investigate tomorrow.
>
> Well, the kernel crashes because xrstor_state() is buggy, Quentin already
> has a fix.
>
> But #GP should be explained...
>

Hopefully the couple of fixes to prevent the #GP should be merged soon, but
they only cure the symptoms and not the root cause of this issue, I think.

Quentin