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SubjectRe: [PATCH 05/16] arm64: Add flags to check the safety of a capability for late CPU
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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 <suzuki.poulose@arm.com>
>>>> ---
>>>> 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

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