From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752742AbeA3O4n (ORCPT ); Tue, 30 Jan 2018 09:56:43 -0500 Received: from foss.arm.com ([217.140.101.70]:54836 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752295AbeA3O4l (ORCPT ); Tue, 30 Jan 2018 09:56:41 -0500 Date: Tue, 30 Jan 2018 14:56:37 +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 05/16] arm64: Add flags to check the safety of a capability for late CPU Message-ID: <20180130145636.GE5862@e103592.cambridge.arm.com> References: <20180123122809.16269-1-suzuki.poulose@arm.com> <20180123122809.16269-6-suzuki.poulose@arm.com> <20180126101020.GM5862@e103592.cambridge.arm.com> <6313a0f1-ed3c-b5b3-7bbd-5f98862a74c6@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6313a0f1-ed3c-b5b3-7bbd-5f98862a74c6@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 30, 2018 at 11:17:38AM +0000, Suzuki K Poulose wrote: > On 26/01/18 10:10, Dave Martin wrote: > >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 > > Sounds better than what I have. I have picked them up. Cool, I had resigned myself to probably not winning that one ;) Cheers ---Dave