From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752903AbeA3PHB (ORCPT ); Tue, 30 Jan 2018 10:07:01 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:54960 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752175AbeA3PG7 (ORCPT ); Tue, 30 Jan 2018 10:06:59 -0500 Subject: Re: [PATCH 05/16] arm64: Add flags to check the safety of a capability for late CPU To: Dave Martin 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 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> <20180130145636.GE5862@e103592.cambridge.arm.com> From: Suzuki K Poulose Message-ID: <50b0c175-0474-e3d7-cdd3-ed2349b4426a@arm.com> Date: Tue, 30 Jan 2018 15:06:56 +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: <20180130145636.GE5862@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 30/01/18 14:56, Dave Martin wrote: > 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 ;) Well, you have won almost all in this series :-) Cheers Suzuki