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=-10.2 required=3.0 tests=BAYES_00, 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 37FB5C4361B for ; Wed, 9 Dec 2020 18:35:17 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A3FB623C90 for ; Wed, 9 Dec 2020 18:35:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A3FB623C90 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E491B8D0035; Wed, 9 Dec 2020 13:35:15 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id DD31B8D0031; Wed, 9 Dec 2020 13:35:15 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C9A3B8D0035; Wed, 9 Dec 2020 13:35:15 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0096.hostedemail.com [216.40.44.96]) by kanga.kvack.org (Postfix) with ESMTP id AF2CC8D0031 for ; Wed, 9 Dec 2020 13:35:15 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 644871EE6 for ; Wed, 9 Dec 2020 18:35:15 +0000 (UTC) X-FDA: 77574596190.20.metal81_05048a7273f1 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin20.hostedemail.com (Postfix) with ESMTP id 3681B180C0609 for ; Wed, 9 Dec 2020 18:35:15 +0000 (UTC) X-HE-Tag: metal81_05048a7273f1 X-Filterd-Recvd-Size: 1948 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Wed, 9 Dec 2020 18:35:14 +0000 (UTC) Date: Wed, 9 Dec 2020 18:35:09 +0000 From: Catalin Marinas To: Will Deacon Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, Jan Kara , Minchan Kim , Andrew Morton , "Kirill A . Shutemov" , Linus Torvalds , Vinayak Menon , kernel-team@android.com Subject: Re: [PATCH 2/2] arm64: mm: Implement arch_wants_old_faultaround_pte() Message-ID: <20201209183509.GH13566@gaia> References: <20201209163950.8494-1-will@kernel.org> <20201209163950.8494-3-will@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201209163950.8494-3-will@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Dec 09, 2020 at 04:39:50PM +0000, Will Deacon wrote: > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h > index da250e4741bd..3424f5881390 100644 > --- a/arch/arm64/include/asm/cpufeature.h > +++ b/arch/arm64/include/asm/cpufeature.h > @@ -764,6 +764,18 @@ static inline bool cpu_has_hw_af(void) > ID_AA64MMFR1_HADBS_SHIFT); > } > > +static inline bool system_has_hw_af(void) > +{ > + u64 mmfr1; > + > + if (!IS_ENABLED(CONFIG_ARM64_HW_AFDBM)) > + return false; > + > + mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1); > + return cpuid_feature_extract_unsigned_field(mmfr1, > + ID_AA64MMFR1_HADBS_SHIFT); > +} Could we not add a new system-wide cpu feature that checks for hardware AF? This read_sanitised_ftr_reg() does a binary search on each invocation. -- Catalin