Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 12 Jan 2021 16:01:06 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc:     Linux PM <linux-pm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        x86 Maintainers <x86@kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Giovanni Gherdovich <ggherdovich@suse.com>,
        Giovanni Gherdovich <ggherdovich@suse.cz>
Subject: Re: [PATCH] x86: PM: Register syscore_ops for scale invariance
Message-ID: <X/25ssA2scFSu+3/@hirez.programming.kicks-ass.net>
References: <1803209.Mvru99baaF@kreacher>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1803209.Mvru99baaF@kreacher>
Precedence: bulk

On Fri, Jan 08, 2021 at 07:05:59PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> On x86 scale invariace tends to be disabled during resume from
> suspend-to-RAM, because the MPERF or APERF MSR values are not as
> expected then due to updates taking place after the platform
> firmware has been invoked to complete the suspend transition.
> 
> That, of course, is not desirable, especially if the schedutil
> scaling governor is in use, because the lack of scale invariance
> causes it to be less reliable.
> 
> To counter that effect, modify init_freq_invariance() to register
> a syscore_ops object for scale invariance with the ->resume callback
> pointing to init_counter_refs() which will run on the CPU starting
> the resume transition (the other CPUs will be taken care of the
> "online" operations taking place later).
> 
> Fixes: e2b0d619b400 ("x86, sched: check for counters overflow in frequency invariant accounting")
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Thanks!, I'll take it through the sched/urgent tree?