On Fri, Mar 27, 2015 at 01:09:24PM +0000, Marc Zyngier wrote:
> Add a new item to the feature set (ARM64_HAS_SYSREG_GIC_CPUIF)
> to indicate that we have a system register GIC CPU interface
>
> This will help KVM switching to alternative instruction patching.
>
> Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>
> Acked-by: Will Deacon <will.deacon@xxxxxxx>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm64/include/asm/cpufeature.h | 8 +++++++-
> arch/arm64/kernel/cpufeature.c | 16 ++++++++++++++++
> 2 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index 6ae35d1..d9e57b5 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -23,8 +23,9 @@
>
> #define ARM64_WORKAROUND_CLEAN_CACHE 0
> #define ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE 1
> +#define ARM64_HAS_SYSREG_GIC_CPUIF 2
>
> -#define ARM64_NCAPS 2
> +#define ARM64_NCAPS 3
>
> #ifndef __ASSEMBLY__
>
> @@ -37,6 +38,11 @@ struct arm64_cpu_capabilities {
> u32 midr_model;
> u32 midr_range_min, midr_range_max;
> };
> +
> + struct { /* Feature register checking */
> + u64 register_mask;
> + u64 register_value;
> + };
> };
> };
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 3d9967e..b0bea2b3 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -22,7 +22,23 @@
> #include <asm/cpu.h>
> #include <asm/cpufeature.h>
>
> +static bool
> +has_id_aa64pfr0_feature(const struct arm64_cpu_capabilities *entry)
> +{
> + u64 val;
> +
> + val = read_cpuid(id_aa64pfr0_el1);
is this preferred compared to fishing it out of cpuinfo ?
> + return (val & entry->register_mask) == entry->register_value;
> +}
> +
> static const struct arm64_cpu_capabilities arm64_features[] = {
> + {
> + .desc = "system register GIC CPU interface",
> + .capability = ARM64_HAS_SYSREG_GIC_CPUIF,
> + .matches = has_id_aa64pfr0_feature,
> + .register_mask = (0xf << 24),
> + .register_value = (1 << 24),
I don't know if it's worth defining these masks in some header file.
The only other place I could see them used was in head.S.
> + },
> {},
> };
>
> --
> 2.1.4
>
Besides the nits, this looks good to me.
-Christoffer
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