linux-kernel - Re: [PATCH] x86/split_lock: Restore warn mode (and add a new one) to avoid userspace regression

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Message-ID: <cc8d0101-73b9-b286-a7a7-e9305cdc1bd9@intel.com>
Date:   Thu, 29 Sep 2022 08:17:07 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>, tony.luck@...el.com,
        tglx@...utronix.de, linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, luto@...nel.org, kernel-dev@...lia.com,
        kernel@...ccoli.net, Fenghua Yu <fenghua.yu@...el.com>,
        Joshua Ashton <joshua@...ggi.es>,
        Paul Gofman <pgofman@...eweavers.com>,
        Pavel Machek <pavel@...x.de>,
        Pierre-Loup Griffais <pgriffais@...vesoftware.com>,
        Melissa Wen <mwen@...lia.com>
Subject: Re: [PATCH] x86/split_lock: Restore warn mode (and add a new one) to
 avoid userspace regression

On 9/29/22 07:57, Guilherme G. Piccoli wrote:
> On 28/09/2022 18:50, Dave Hansen wrote:
>> [...]
>> It boils down to either:
>>  * The misery is good and we keep it as-is, or
>>  * The misery is bad and we kill it
>>
>> My gut says we should keep the warnings and kill the misery.  The folks
>> who are going to be able to fix the issues are probably also the ones
>> looking at dmesg and don't need the extra hint from the misery.  The
>> folks running Windows games don't look at dmesg and just want to play
>> their game without misery.
>>
> Hi Dave, thanks for your response. I really appreciated your reasoning,
> and I think it's a good argument. In the end, adding misery would harm
> the users that are unlikely to be able to fix (or at least, fix quickly)
> the split lock situation, like games or legacy/proprietary code.
> 
> I have a revert removing the misery ready and tested, let me know if I
> should submit it.

I'm a bit of a late arrival to the split lock party, so I'm a bit
hesitant to merge any changes immediately.

How about we give it a few weeks and see if the current behavior impacts
anyone else?  Maybe the best route will be more clear then.