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From: Andy Lutomirski <luto@amacapital.net>
Date: Mon, 5 Jan 2015 13:54:40 -0800
Message-ID: <CALCETrV6=aWoAckieQkPJ4BCr9VzU=9080EmLfeL4ZWm+Hr55g@mail.gmail.com>
Subject: Re: [PATCH v4 2/5] x86, traps: Track entry into and exit from IST context
To: Tony Luck <tony.luck@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>, Paul McKenney <paulmck@linux.vnet.ibm.com>,
        X86 ML <x86@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, Oleg Nesterov <oleg@redhat.com>,
        Andi Kleen <andi@firstfloor.org>,
        Josh Triplett <josh@joshtriplett.org>,
        =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= <fweisbec@gmail.com>
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On Mon, Jan 5, 2015 at 1:46 PM, Tony Luck <tony.luck@gmail.com> wrote:
> On Wed, Dec 10, 2014 at 4:24 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>> I think you need ist_begin_non_atomic() before local_irq_enable() and
>> ist_end_non_atomic() after local_irq_disable().  Otherwise it should
>> be good.
>
> In your x86/paranoid branch you added:
>
>      prev_state = ist_enter(regs);
>           .... body of do_machine_check() here ...
>      ist_exit(regs, prev_state);
>
> Does that override the previous advice? Or do I still need something before
> I call local_irq_enable() and after local_irq_disable()?

I think I was just being vague.  It would be:

     prev_state = ist_enter(regs);
          .... beginning of do_machine_check() here ...

     if (whatever condition) {
        ist_begin_non_atomic();
        local_irq_enable();

        ...

        local_irq_disable();
        ist_end_non_atomic();
     ist_exit(regs, prev_state);

--Andy

>
> -Tony



-- 
Andy Lutomirski
AMA Capital Management, LLC