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.poul...@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
might be easier to understand.
[...]
Cheers
---Dave
