From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751611AbeA3LRn (ORCPT ); Tue, 30 Jan 2018 06:17:43 -0500 Received: from foss.arm.com ([217.140.101.70]:52324 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751219AbeA3LRm (ORCPT ); Tue, 30 Jan 2018 06:17:42 -0500 Subject: Re: [PATCH 05/16] arm64: Add flags to check the safety of a capability for late CPU To: Dave Martin 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 References: <20180123122809.16269-1-suzuki.poulose@arm.com> <20180123122809.16269-6-suzuki.poulose@arm.com> <20180126101020.GM5862@e103592.cambridge.arm.com> From: Suzuki K Poulose Message-ID: <6313a0f1-ed3c-b5b3-7bbd-5f98862a74c6@arm.com> Date: Tue, 30 Jan 2018 11:17:38 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <20180126101020.GM5862@e103592.cambridge.arm.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Cheers Suzuki