From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752660AbeAZKK1 (ORCPT ); Fri, 26 Jan 2018 05:10:27 -0500 Received: from foss.arm.com ([217.140.101.70]:44586 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751606AbeAZKK0 (ORCPT ); Fri, 26 Jan 2018 05:10:26 -0500 Date: Fri, 26 Jan 2018 10:10:21 +0000 From: Dave Martin To: Suzuki K Poulose Cc: linux-arm-kernel@lists.infradead.org, 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 Subject: Re: [PATCH 05/16] arm64: Add flags to check the safety of a capability for late CPU Message-ID: <20180126101020.GM5862@e103592.cambridge.arm.com> References: <20180123122809.16269-1-suzuki.poulose@arm.com> <20180123122809.16269-6-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180123122809.16269-6-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 Tue, Jan 23, 2018 at 12:27:58PM +0000, Suzuki K Poulose wrote: > Add two different flags to indicate if the conflict of a capability > on a late CPU with the current system state > > 1) Can a CPU have a capability when the system doesn't have it ? > > Most arm64 features could have this set. While erratum work arounds > cannot have this, as we may miss work arounds. > > 2) Can a CPU miss a capability when the system has it ? > This could be set for arm64 erratum work arounds as we don't > care if a CPU doesn't need the work around. However it should > be clear for features. > > These flags could be added to certain entries based on their nature. > > Signed-off-by: Suzuki K Poulose > --- > arch/arm64/include/asm/cpufeature.h | 35 +++++++++++++++++++++++++++++++---- > 1 file changed, 31 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h > index 4fd5de8ef33e..27d037bb0451 100644 > --- a/arch/arm64/include/asm/cpufeature.h > +++ b/arch/arm64/include/asm/cpufeature.h > @@ -94,10 +94,25 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; > #define SCOPE_SYSTEM ARM64_CPUCAP_SCOPE_SYSTEM > #define SCOPE_LOCAL_CPU ARM64_CPUCAP_SCOPE_LOCAL_CPU > > -/* CPU errata detected at boot time based on feature of one or more CPUs */ > -#define ARM64_CPUCAP_STRICT_CPU_LOCAL_ERRATUM (ARM64_CPUCAP_SCOPE_LOCAL_CPU) > -/* CPU feature detected at boot time based on system-wide value of a feature */ > -#define ARM64_CPUCAP_BOOT_SYSTEM_FEATURE (ARM64_CPUCAP_SCOPE_SYSTEM) > +/* Is it safe for a late CPU to have this capability when system doesn't already have */ > +#define ARM64_CPUCAP_LATE_CPU_SAFE_TO_HAVE BIT(2) > +/* Is it safe for a late CPU to miss this capability when system has it */ > +#define ARM64_CPUCAP_LATE_CPU_SAFE_TO_MISS BIT(3) Maybe _OPTIONAL and _PERMITTED would be a bit less verbose? Alternatively, ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU might be easier to understand. [...] Cheers ---Dave