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SubjectRe: [PATCH v3 3/7] arm64: kpti: move check for non-vulnerable CPUs to a function
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Hi Jeremy,

On 09/01/2019 23:55, Jeremy Linton wrote:
> From: Mian Yousaf Kaukab <ykaukab@suse.de>
>
> Add is_meltdown_safe() which is a whitelist of known safe cores.
>
> Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
> [Moved location of function]
> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
> ---
> arch/arm64/kernel/cpufeature.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 4f272399de89..ab784d7a0083 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -947,8 +947,7 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope)
> #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
> static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */
>
> -static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
> - int scope)
> +static bool is_cpu_meltdown_safe(void)
> {
> /* List of CPUs that are not vulnerable and don't need KPTI */
> static const struct midr_range kpti_safe_list[] = {
> @@ -962,6 +961,15 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
> MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
> { /* sentinel */ }
> };
> + if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list))

nit: Does it make sense to rename the list to "meltdown_safe_list", to match the
function name ?

Also also, you may do :

return is_midr_in_range_list(read_cpuid_id(), kpti_safe_list);

Either way

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

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