Re: [PATCH 24/27] arm64/sve: Detect SVE and activate runtime support

[Suzuki K Poulose <Suzuki dot Poulose at arm dot com>]

On 09/08/17 13:05, Dave Martin wrote:
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>
> This patch enables detection of hardware SVE support via the
> cpufeatures framework, and reports its presence to the kernel and
> userspace via the new ARM64_SVE cpucap and HWCAP_SVE hwcap
> respectively.
>
> Userspace can also detect SVE using ID_AA64PFR0_EL1, using the
> cpufeatures MRS emulation.
>
> When running on hardware that supports SVE, this enables runtime
> kernel support for SVE, and allows user tasks to execute SVE
> instructions and make of the of the SVE-specific user/kernel
> interface extensions implemented by this series.
>
> Signed-off-by: Dave Martin <Dave.Martin@arm.com>


> ---
>  arch/arm64/include/asm/cpucaps.h    |  3 ++-
>  arch/arm64/include/asm/cpufeature.h |  3 ++-
>  arch/arm64/include/uapi/asm/hwcap.h |  1 +
>  arch/arm64/kernel/cpufeature.c      | 16 ++++++++++++++++
>  arch/arm64/kernel/cpuinfo.c         |  1 +
>  5 files changed, 22 insertions(+), 2 deletions(-)

...

> @@ -944,6 +957,9 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
>         HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_JSCVT_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_JSCVT),
>         HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_FCMA_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_FCMA),
>         HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_LRCPC_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_LRCPC),
> +#ifdef CONFIG_ARM64_SVE
> +       HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_SVE_SHIFT, FTR_UNSIGNED, ID_AA64PFR0_SVE, CAP_HWCAP, HWCAP_SVE),
> +#endif
>         {},
>  };
>
> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
> index 0e087d7..943aad0 100644
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -69,6 +69,7 @@ static const char *const hwcap_str[] = {
>         "jscvt",
>         "fcma",
>         "lrcpc",
> +       "sve",
>         NULL
>  };


Dave,

Could you please update the Documentation for the exposed CPU feature
registers to include the SVE field ? Rest looks good to me. With that
change,

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>