linux-kernel - Re: [patch V4 part 1 29/36] x86/mce: Send #MC singal from task work

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Message-ID: <1278452779.21179.1589472210183.JavaMail.zimbra@efficios.com>
Date:   Thu, 14 May 2020 12:03:30 -0400 (EDT)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        x86 <x86@...nel.org>, paulmck <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>, rostedt <rostedt@...dmis.org>,
        "Joel Fernandes, Google" <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Tony Luck <tony.luck@...el.com>
Subject: Re: [patch V4 part 1 29/36] x86/mce: Send #MC singal from task work

----- On May 14, 2020, at 10:17 AM, Borislav Petkov bp@...en8.de wrote:

> + Tony.
> 
> On Tue, May 05, 2020 at 03:16:31PM +0200, Thomas Gleixner wrote:
>> From: Peter Zijlstra <peterz@...radead.org>
>> 
>> Convert #MC over to using task_work_add(); it will run the same code
>> slightly later, on the return to user path of the same exception.
>> 
>> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
>> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
>> Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
>> ---
>>  arch/x86/kernel/cpu/mce/core.c |   56 ++++++++++++++++++++++-------------------
>>  include/linux/sched.h          |    6 ++++
>>  2 files changed, 37 insertions(+), 25 deletions(-)
> 
> I like this:
> 
> Reviewed-by: Borislav Petkov <bp@...e.de>

What I am not fully grasping here is whether this patch preserves the instruction
pointer (and possibly other relevant information for siginfo_t) triggering the
exception in a scenario where we have:

- #MC triggered, queuing task work,
- unrelated signal happens to be delivered to task,
- exit to usermode loop handles do_signal first,
- then it runs task work.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com