linux-kernel - Re: [PATCH v4] x86/power: Fix 'nosmt' vs. hibernation triple fault during resume

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Message-ID: <20190531161952.dps3grwg4ytrpuqw@treble>
Date:   Fri, 31 May 2019 11:19:52 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Andy Lutomirski <luto@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        the arch/x86 maintainers <x86@...nel.org>,
        Pavel Machek <pavel@....cz>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] x86/power: Fix 'nosmt' vs. hibernation triple fault
 during resume

On Fri, May 31, 2019 at 05:41:18PM +0200, Jiri Kosina wrote:
> On Fri, 31 May 2019, Josh Poimboeuf wrote:
> 
> > The only question I'd have is if we have data on the power savings 
> > difference between hlt and mwait.  mwait seems to wake up on a lot of 
> > different conditions which might negate its deeper sleep state.
> 
> hlt wakes up on basically the same set of events, but has the 
> auto-restarting semantics on some of them (especially SMM). So the wakeup 
> frequency itself shouldn't really contribute to power consumption 
> difference; it's the C-state that mwait allows CPU to enter.

Ok.  I reluctantly surrender :-)  For your v4:

  Reviewed-by: Josh Poimboeuf <jpoimboe@...hat.com>

It works as a short term fix, but it's fragile, and it does feel like
we're just adding more duct tape, as Andy said.

-- 
Josh