linux-kernel - Re: [RFC PATCH 23/23] x86/process: Reset hardware history in context switch

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Message-ID: <20221003194935.GA20128@ranerica-svr.sc.intel.com>
Date:   Mon, 3 Oct 2022 12:49:35 -0700
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Ricardo Neri <ricardo.neri@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Len Brown <len.brown@...el.com>, Mel Gorman <mgorman@...e.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Valentin Schneider <vschneid@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, "Tim C . Chen" <tim.c.chen@...el.com>
Subject: Re: [RFC PATCH 23/23] x86/process: Reset hardware history in context
 switch

On Mon, Oct 03, 2022 at 12:15:32AM +0200, Borislav Petkov wrote:
> On Sun, Oct 02, 2022 at 03:12:38PM -0700, Ricardo Neri wrote:
> > Sure I can do this, Boris. I guess this implies that I also need to
> > add the DISABLE_MASK bits.
> 
> Are you adding a CONFIG_ item which can control the DISABLE_MASK bit
> too?

I am not. I could use CONFIG_INTEL_HFI_THERMAL, as using HRESET only makes
sense when Intel Thread Director (Peter argued in separate email against
having a config option specific for Intel Thread Director).

> 
> > Othewise, IIUC, cpu_feature_enabled() falls back to static_cpu_has().
> 
> And?

Since I did not implement a DISABLE_MASK bit nor a CONFIG_ option for
HRESET, I thought that static_cpu_has() was sufficient.

I am not against using cpu_feature_enabled(), I just want to confirm that
I also need to implement the DISABLE_MASK bit and the CONFIG_ option.

Thanks and BR,
Ricardo