From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751998AbeBHQKV (ORCPT ); Thu, 8 Feb 2018 11:10:21 -0500 Received: from foss.arm.com ([217.140.101.70]:37012 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750929AbeBHQKU (ORCPT ); Thu, 8 Feb 2018 11:10:20 -0500 Date: Thu, 8 Feb 2018 16:10:16 +0000 From: Dave Martin To: Suzuki K Poulose Cc: mark.rutland@arm.com, ckadabi@codeaurora.org, ard.biesheuvel@linaro.org, marc.zyngier@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, jnair@caviumnetworks.com, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 1/2] arm64: capabilities: Allow flexibility in scope Message-ID: <20180208161015.GZ5862@e103592.cambridge.arm.com> References: <86f23003-72bc-5bfc-af40-a92cc68def45@arm.com> <20180208121238.18792-1-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180208121238.18792-1-suzuki.poulose@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 08, 2018 at 12:12:37PM +0000, Suzuki K Poulose wrote: > So far we have restricted the scopes for the capabilities > as follows : > 1) Errata workaround check are run all CPUs (i.e, always > SCOPE_LOCAL_CPU) > 2) Arm64 features are run only once after the sanitised > feature registers are available using the SCOPE_SYSTEM. > > This prevents detecting cpu features that can be detected > on one or more CPUs with SCOPE_LOCAL_CPU (e.g KPTI). Similarly > for errata workaround with SCOPE_SYSTEM. > > This patch makes sure that we allow flexibility of having > any scope for a capability. So, we now run through both > arm64_features and arm64_errata in two phases for detection: > > a) with SCOPE_LOCAL_CPU filter on each boot time enabled > CPUs. > b) with SCOPE_SYSTEM filter only once after all boot time > enabled CPUs are active. > > Cc: Dave Martin > Signed-off-by: Suzuki K Poulose > --- > arch/arm64/kernel/cpufeature.c | 33 ++++++++++++++++++++++++--------- > 1 file changed, 24 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 61d4c3cfb1cc..e1a56fa889a5 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -505,6 +505,7 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) > > extern const struct arm64_cpu_capabilities arm64_errata[]; > static void update_cpu_errata_workarounds(void); > +static void update_cpu_local_features(void); > > void __init init_cpu_features(struct cpuinfo_arm64 *info) > { > @@ -554,6 +555,7 @@ void __init init_cpu_features(struct cpuinfo_arm64 *info) > * initialised the cpu feature infrastructure. > */ > update_cpu_errata_workarounds(); > + update_cpu_local_features(); > } > > static void update_cpu_ftr_reg(struct arm64_ftr_reg *reg, u64 new) > @@ -1387,13 +1389,15 @@ static void verify_local_cpu_errata_workarounds(void) > static void update_cpu_errata_workarounds(void) > { > update_cpu_capabilities(arm64_errata, > - ARM64_CPUCAP_SCOPE_ALL, > + ARM64_CPUCAP_SCOPE_LOCAL_CPU, In isolation, this looks strange because it seems to handle only a subset of arm64_errata now. I think I understand the change as follows: * all previously-existing errata workarounds SCOPE_LOCAL_CPU anyway, so the behavior here doesn't change for any existing caps; * the non SCOPE_SYSTEM workarounds (which this patch prepares for) are handled by the new setup_errata_workaround() path. Similarly, the features handling is split into two: one mirroring the current behaviour (for SCOPE_SYSTEM this time) and one handling the rest, for supporting SCOPE_CPU_LOCAL features in subsequent patches. Does that sound right? I'm not sure we need extra comments or documentation; I just want to check that I've understood the patch correctly. Cheers ---Dave > "enabling workaround for"); > } > > -static void __init enable_errata_workarounds(void) > +static void update_cpu_local_features(void) > { > - enable_cpu_capabilities(arm64_errata, ARM64_CPUCAP_SCOPE_ALL); > + update_cpu_capabilities(arm64_features, > + ARM64_CPUCAP_SCOPE_LOCAL_CPU, > + "detected feature:"); > } > > /* > @@ -1430,23 +1434,34 @@ void check_local_cpu_capabilities(void) > > /* > * If we haven't finalised the system capabilities, this CPU gets > - * a chance to update the errata work arounds. > + * a chance to update the errata work arounds and local CPU features. > * Otherwise, this CPU should verify that it has all the system > * advertised capabilities. > */ > - if (!sys_caps_initialised) > + if (!sys_caps_initialised) { > update_cpu_errata_workarounds(); > - else > + update_cpu_local_features(); > + } else { > verify_local_cpu_capabilities(); > + } > } > > static void __init setup_feature_capabilities(void) > { > update_cpu_capabilities(arm64_features, > - ARM64_CPUCAP_SCOPE_ALL, "detected feature:"); > + ARM64_CPUCAP_SCOPE_SYSTEM, > + "detected feature:"); > enable_cpu_capabilities(arm64_features, ARM64_CPUCAP_SCOPE_ALL); > } > > +static void __init setup_errata_workarounds(void) > +{ > + update_cpu_capabilities(arm64_errata, > + ARM64_CPUCAP_SCOPE_SYSTEM, > + "enabling workaround for"); > + enable_cpu_capabilities(arm64_errata, ARM64_CPUCAP_SCOPE_ALL); > +} > + > DEFINE_STATIC_KEY_FALSE(arm64_const_caps_ready); > EXPORT_SYMBOL(arm64_const_caps_ready); > > @@ -1468,9 +1483,9 @@ void __init setup_cpu_features(void) > u32 cwg; > int cls; > > - /* Set the CPU feature capabilies */ > + /* Finalise the CPU capabilities */ > setup_feature_capabilities(); > - enable_errata_workarounds(); > + setup_errata_workarounds(); > mark_const_caps_ready(); > setup_elf_hwcaps(arm64_elf_hwcaps); > > -- > 2.14.3 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel