linux-kernel - Re: [PATCH v2] xen/pv: Fix a boot up hang revealed by int3 self test

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Message-ID: <20190712130916.GR3419@hirez.programming.kicks-ass.net>
Date:   Fri, 12 Jul 2019 15:09:16 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Zhenzhong Duan <zhenzhong.duan@...cle.com>
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        x86@...nel.org, srinivas.eeda@...cle.com,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v2] xen/pv: Fix a boot up hang revealed by int3 self test

On Fri, Jul 12, 2019 at 09:04:22PM +0800, Zhenzhong Duan wrote:
> 
> On 2019/7/12 20:06, Peter Zijlstra wrote:
> > On Thu, Jul 11, 2019 at 04:15:21PM +0800, Zhenzhong Duan wrote:
> > > diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
> > > index 4722ba2..2138d69 100644
> > > --- a/arch/x86/xen/enlighten_pv.c
> > > +++ b/arch/x86/xen/enlighten_pv.c
> > > @@ -596,7 +596,7 @@ struct trap_array_entry {
> > >   static struct trap_array_entry trap_array[] = {
> > >   	{ debug,                       xen_xendebug,                    true },
> > > -	{ int3,                        xen_xenint3,                     true },
> > > +	{ int3,                        xen_int3,                        true },
> > >   	{ double_fault,                xen_double_fault,                true },
> > >   #ifdef CONFIG_X86_MCE
> > >   	{ machine_check,               xen_machine_check,               true },
> > I'm confused on the purpose of trap_array[], could you elucidate me?
> 
> Used to replace trap handler addresses by Xen specific ones and sanity check
> 
> if there's an unexpected IST-using fault handler.

git grep xen_int3, failed me. Where does that symbol come from?

> > The sole user seems to be get_trap_addr() and that talks about ISTs, but
> > #BP isn't an IST anymore, so why does it have ist_okay=true?
> 
> Oh, yes, I missed that boolean, thanks. I'll try ist_okey=false for int3 and
> test it tomorrow.

Thanks!