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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id u19sm5575133wmu.41.2019.05.30.00.47.12 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Thu, 30 May 2019 00:47:13 -0700 (PDT) Date: Thu, 30 May 2019 09:47:10 +0200 From: Ingo Molnar To: "Rafael J. Wysocki" Cc: x86 , Linux PM , Ido Schimmel , LKML , Len Brown , Srinivas Pandruvada , Laura Abbott , Thomas Gleixner , Peter Zijlstra , Simon Schricker , Borislav Petkov , Hannes Reinecke Subject: Re: [PATCH] x86: intel_epb: Do not build when CONFIG_PM is unset Message-ID: <20190530074710.GA68696@gmail.com> References: <1637073.gl2OfxWTjI@aspire.rjw.lan> <1627338.1fd8ofggM8@kreacher> <20190509174338.GA24432@splinter> <3844875.YPkTDDlcrF@kreacher> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3844875.YPkTDDlcrF@kreacher> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Rafael J. Wysocki wrote: > From: Rafael J. Wysocki > > Commit 9ed0985332a6 ("x86: intel_epb: Take CONFIG_PM into account") > prevented the majority of the Performance and Energy Bias Hint (EPB) > handling code from being built when CONFIG_PM is unset to fix a > regression introduced by commit b9c273babce7 ("PM / arch: x86: > MSR_IA32_ENERGY_PERF_BIAS sysfs interface"). > > In hindsight, however, it would be better to skip all of the EPB > handling code for CONFIG_PM unset as there really is no reason for > it to be there in that case. Namely, if the EPB is not touched > by the kernel at all with CONFIG_PM unset, there is no need to > worry about modifying the EPB inadvertently on CPU online and since > the system will not suspend or hibernate then, there is no need to > worry about possible modifications of the EPB by the platform > firmware during system-wide PM transitions. > > For this reason, revert the changes made by commit 9ed0985332a6 > and only allow intel_epb.o to be built when CONFIG_PM is set. > > Note that this changes the behavior of the kernels built with > CONFIG_PM unset as they will not modify the EPB on boot if it is > zero initially any more, so it is not a fix strictly speaking, but > users building their kernels with CONFIG_PM unset really should not > expect them to take energy efficiency into account. Moreover, if > CONFIG_PM is unset for performance reasons, leaving EPB as set > initially by the platform firmware will actually be consistent > with the user's expectations. > > Signed-off-by: Rafael J. Wysocki > --- > > This is complementary to the EPB handling changes made in the current > development cycle, so IMO it would be good to do it in this cycle too > if there are no technical concerns or objections regarding it. Sure: Acked-by: Ingo Molnar Thanks, Ingo