by Suzuki K Poulose

[permalink] [raw]

Subject: Re: [PATCH 03/11] arm64: Take into account ID_AA64PFR0_EL1.CSV3

On 04/01/18 15:08, Will Deacon wrote:
> For non-KASLR kernels where the KPTI behaviour has not been overridden
> on the command line we can use ID_AA64PFR0_EL1.CSV3 to determine whether
> or not we should unmap the kernel whilst running at EL0.
>
> Signed-off-by: Will Deacon <[email protected]>
> ---
> arch/arm64/include/asm/sysreg.h | 1 +
> arch/arm64/kernel/cpufeature.c | 7 ++++++-
> 2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 08cc88574659..ae519bbd3f9e 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -437,6 +437,7 @@
> #define ID_AA64ISAR1_DPB_SHIFT 0
>
> /* id_aa64pfr0 */
> +#define ID_AA64PFR0_CSV3_SHIFT 60
> #define ID_AA64PFR0_SVE_SHIFT 32
> #define ID_AA64PFR0_GIC_SHIFT 24
> #define ID_AA64PFR0_ASIMD_SHIFT 20
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 9f0545dfe497..e11c11bb5b02 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -145,6 +145,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
> };
>
> static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
> + ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV3_SHIFT, 4, 0),
> ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_SVE_SHIFT, 4, 0),
> ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_GIC_SHIFT, 4, 0),
> S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_ASIMD_SHIFT, 4, ID_AA64PFR0_ASIMD_NI),
> @@ -851,6 +852,8 @@ 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 __unused)
> {
> + u64 pfr0 = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
> +
> /* Forced on command line? */
> if (__kpti_forced) {
> pr_info_once("kernel page table isolation forced %s by command line option\n",
> @@ -862,7 +865,9 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
> if (IS_ENABLED(CONFIG_RANDOMIZE_BASE))
> return true;
>
> - return false;
> + /* Defer to CPU feature registers */
> + return !cpuid_feature_extract_unsigned_field(pfr0,
> + ID_AA64PFR0_CSV3_SHIFT);
> }
>

The cpufeature bit changes look good to me. FWIW,

Reviewed-by: Suzuki K Poulose <[email protected]>

2018-01-05 10:29:26

by Suzuki K Poulose

[permalink] [raw]

Subject: Re: [PATCH 04/11] arm64: cpufeature: Pass capability structure to ->enable callback

On 04/01/18 15:08, Will Deacon wrote:
> In order to invoke the CPU capability ->matches callback from the ->enable
> callback for applying local-CPU workarounds, we need a handle on the
> capability structure.
>
> This patch passes a pointer to the capability structure to the ->enable
> callback.
>
> Signed-off-by: Will Deacon <[email protected]>
> ---
> arch/arm64/kernel/cpufeature.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index e11c11bb5b02..6133c14b9b01 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1151,7 +1151,7 @@ void __init enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps)
> * uses an IPI, giving us a PSTATE that disappears when
> * we return.
> */
> - stop_machine(caps->enable, NULL, cpu_online_mask);
> + stop_machine(caps->enable, (void *)caps, cpu_online_mask);
> }
> }
> }
> @@ -1194,7 +1194,7 @@ verify_local_cpu_features(const struct arm64_cpu_capabilities *caps)
> cpu_die_early();
> }
> if (caps->enable)
> - caps->enable(NULL);
> + caps->enable((void *)caps);
> }
> }
>
>

Reviewed-by: Suzuki K Poulose <[email protected]>