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=unavailable 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 639FAC433FE for ; Wed, 9 Dec 2020 18:35:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 39B6823C8F for ; Wed, 9 Dec 2020 18:35:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733136AbgLISfy (ORCPT ); Wed, 9 Dec 2020 13:35:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:37962 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733046AbgLISfy (ORCPT ); Wed, 9 Dec 2020 13:35:54 -0500 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) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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