From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933186AbeCMLwO (ORCPT ); Tue, 13 Mar 2018 07:52:14 -0400 Received: from foss.arm.com ([217.140.101.70]:36478 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933051AbeCMLwM (ORCPT ); Tue, 13 Mar 2018 07:52:12 -0400 From: Suzuki K Poulose To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, will.deacon@arm.com, dave.martin@arm.com, catalin.marinas@arm.com, marc.zyngier@arm.com, mark.rutland@arm.com, ard.biesheuvel@linaro.org, jnair@caviumnetworks.com, ckadabi@codeaurora.org, robin.murphy@arm.com, shankerd@codeaurora.org, Suzuki K Poulose Subject: [PATCH v4 12/22] arm64: capabilities: Introduce weak features based on local CPU Date: Tue, 13 Mar 2018 11:51:10 +0000 Message-Id: <20180313115120.17256-13-suzuki.poulose@arm.com> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180313115120.17256-1-suzuki.poulose@arm.com> References: <20180313115120.17256-1-suzuki.poulose@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Now that we have the flexibility of defining system features based on individual CPUs, introduce CPU feature type that can be detected on a local SCOPE and ignores the conflict on late CPUs. This is applicable for ARM64_HAS_NO_HW_PREFETCH, where it is fine for the system to have CPUs without hardware prefetch turning up later. We only suffer a performance penalty, nothing fatal. Cc: Will Deacon Reviewed-by: Dave Martin Signed-off-by: Suzuki K Poulose --- arch/arm64/include/asm/cpufeature.h | 8 ++++++++ arch/arm64/kernel/cpufeature.c | 2 +- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index c187b926daf9..effb1c038221 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -239,6 +239,14 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; */ #define ARM64_CPUCAP_SYSTEM_FEATURE \ (ARM64_CPUCAP_SCOPE_SYSTEM | ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU) +/* + * CPU feature detected at boot time based on feature of one or more CPUs. + * All possible conflicts for a late CPU are ignored. + */ +#define ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE \ + (ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ + ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU | \ + ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU) struct arm64_cpu_capabilities { const char *desc; diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index fc6164bc9ef4..0955e02fa638 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1007,7 +1007,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = { { .desc = "Software prefetching using PRFM", .capability = ARM64_HAS_NO_HW_PREFETCH, - .type = ARM64_CPUCAP_SYSTEM_FEATURE, + .type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE, .matches = has_no_hw_prefetch, }, #ifdef CONFIG_ARM64_UAO -- 2.14.3