Re: 4.15-rc6+ hang

[Tom Hromatka]

On 01/04/2018 07:22 PM, Linus Torvalds wrote:
> On Thu, Jan 4, 2018 at 5:36 PM, Tom Hromatka <tom.hromatka@xxxxxxxxxx> 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.

Yes, I can try and bisect this.

> > 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

pti=no also hung in the same fashion with the 4.15-rc6+
kernel.

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

4.15-rc5 hung as well. I'll go further back and see what I
can find.

> > [    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.

It seems probable that this is a VirtualBox issue. I was
able to boot my exact 4.15-rc6+ kernel in qemu-kvm v1.5.3
just fine.

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

4.15-rc5 also exhibits the xsave issue in VirtualBox.

Thanks.

Tom

>                    Linus