From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2C7CC4CEC9 for ; Wed, 18 Sep 2019 16:45:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A6996214AF for ; Wed, 18 Sep 2019 16:45:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387732AbfIRQpw (ORCPT ); Wed, 18 Sep 2019 12:45:52 -0400 Received: from foss.arm.com ([217.140.110.172]:45048 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728817AbfIRQpw (ORCPT ); Wed, 18 Sep 2019 12:45:52 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B8647337; Wed, 18 Sep 2019 09:45:51 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1356A3F59C; Wed, 18 Sep 2019 09:45:48 -0700 (PDT) Date: Wed, 18 Sep 2019 17:45:47 +0100 From: Catalin Marinas To: Suzuki K Poulose Cc: Jia He , Will Deacon , Mark Rutland , James Morse , Marc Zyngier , Matthew Wilcox , "Kirill A. Shutemov" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Punit Agrawal , Anshuman Khandual , Jun Yao , Alex Van Brunt , Robin Murphy , Thomas Gleixner , Andrew Morton , =?iso-8859-1?B?Suly9G1l?= Glisse , Ralph Campbell , hejianet@gmail.com, Kaly Xin Subject: Re: [PATCH v4 1/3] arm64: cpufeature: introduce helper cpu_has_hw_af() Message-ID: <20190918164546.GA41588@arrakis.emea.arm.com> References: <20190918131914.38081-1-justin.he@arm.com> <20190918131914.38081-2-justin.he@arm.com> <78881acb-5871-9534-c8cc-6f54937be3fd@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <78881acb-5871-9534-c8cc-6f54937be3fd@arm.com> 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 On Wed, Sep 18, 2019 at 03:20:41PM +0100, Suzuki K Poulose wrote: > On 18/09/2019 14:19, Jia He wrote: > > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h > > index c96ffa4722d3..206b6e3954cf 100644 > > --- a/arch/arm64/include/asm/cpufeature.h > > +++ b/arch/arm64/include/asm/cpufeature.h > > @@ -390,6 +390,7 @@ extern DECLARE_BITMAP(boot_capabilities, ARM64_NPATCHABLE); > > for_each_set_bit(cap, cpu_hwcaps, ARM64_NCAPS) > > bool this_cpu_has_cap(unsigned int cap); > > +bool cpu_has_hw_af(void); > > void cpu_set_feature(unsigned int num); > > bool cpu_have_feature(unsigned int num); > > unsigned long cpu_get_elf_hwcap(void); > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > > index b1fdc486aed8..c5097f58649d 100644 > > --- a/arch/arm64/kernel/cpufeature.c > > +++ b/arch/arm64/kernel/cpufeature.c > > @@ -1141,6 +1141,12 @@ static bool has_hw_dbm(const struct arm64_cpu_capabilities *cap, > > return true; > > } > > +/* Decouple AF from AFDBM. */ > > +bool cpu_has_hw_af(void) > > +{ > Sorry for not having asked this earlier. Are we interested in, > > "whether *this* CPU has AF support ?" or "whether *at least one* > CPU has the AF support" ? The following code does the former. > > > + return (read_cpuid(ID_AA64MMFR1_EL1) & 0xf); In a non-preemptible context, the former is ok (per-CPU). -- Catalin