linux-kernel - Re: 4.15-rc6+ hang

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Date:   Thu, 4 Jan 2018 18:22:58 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Tom Hromatka <tom.hromatka@...cle.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Dhaval Giani <dhaval.giani@...cle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: 4.15-rc6+ hang

On Thu, Jan 4, 2018 at 5:36 PM, Tom Hromatka <tom.hromatka@...cle.com> wrote:
> I am seeing a hang running kernel 4.15-rc6+ on a vanilla VirtualBox VM.
> (VirtualBox version 5.0.40)

Any chance of bisecting this?

I could imagine that all the stuff we now do for page table isolation
might confuse the VM.

> When I boot this kernel, it hangs and falls back into dracut. Here's
> the boot log immediately prior to the hang:

So a few questions:

 (a) does it work with "pti=no" on the kernel command line

 (b) what was the last kernel that worked? Is 4.15-rc5 fine, for example?

> [    0.000000] ------------[ cut here ]------------
> [    0.000000] XSAVE consistency problem, dumping leaves

I think this is a vbox issue, with virtualbox not exposing all the
xsave state, so that when the kernel adds up the xsave areas, the end
result doesn't match what the total size is reported to be.

I suspect you _should_ have gotten that before too, independently of the hang.

                  Linus