linux-kernel - Re: [PATCH v2 00/18] Entry stack switching

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Date:   Thu, 23 Nov 2017 07:58:28 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>, X86 ML <x86@...nel.org>,
        Borislav Petkov <bpetkov@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH v2 00/18] Entry stack switching


* Ingo Molnar <mingo@...nel.org> wrote:

> 
> * Ingo Molnar <mingo@...nel.org> wrote:
> 
> > > Anyway, I booted your config (more or less -- I munged it through
> > > virtme-configkernel --update first) with 17 vCPUs and it seems fine.
> > > Is the issue reliable enough to bisect?
> > 
> > Ok, it should be bisectable, will try to bisect it.
> 
> The latestest entry-stack code appears to be working fine though.
> 
> So one of the below fixes from yesterday appears to have done the trick.
> 
> I'll re-test today to make sure: maybe it's more sporadic than I thought, in one 
> of the bootups I got the do_IRQ warning only once, in half a day of uptime.

I re-tested and it all seems fine now. I suspect it got fixed by:

  ca37e57bbe0c: x86/entry/64: Add missing irqflags tracing to native_load_gs_index()

still it is weird, because I boot that system with latest -tip on a daily basis, 
and don't remember having seen that warning.

Do you have any theory for why the entry stack changes would uncover this bug?

Thanks,

	Ingo