Re: [PATCH v2 15/20] arm64: capabilities: Add support for checks based on a list of MIDRs

From: Dave Martin
Date: Wed Feb 07 2018 - 05:39:35 EST

On Wed, Jan 31, 2018 at 06:28:02PM +0000, Suzuki K Poulose wrote:
> Add helpers for detecting an errata on list of midr ranges
> of affected CPUs, with the same work around.

Reviewed-by: Dave Martin <Dave.Martin@xxxxxxx>

> Cc: Will Deacon <will.deacon@xxxxxxx>
> Cc: Dave Martin <dave.martin@xxxxxxx>
> Cc: Mark Rutland <mark.rutland@xxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
> arch/arm64/include/asm/cpufeature.h | 1 +
> arch/arm64/kernel/cpu_errata.c | 61 +++++++++++++++++++++----------------
> arch/arm64/kernel/cpufeature.c | 10 +++---
> 3 files changed, 42 insertions(+), 30 deletions(-)
>
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index 0cfe42c3225c..462c35d1a38c 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -281,6 +281,7 @@ struct arm64_cpu_capabilities {
> void (*cpu_enable)(const struct arm64_cpu_capabilities *cap);
> union {
> struct midr_range midr_range; /* To be used for erratum handling only */
> + const struct midr_range *midr_range_list;
> struct { /* Feature register checking */
> u32 sys_reg;
> u8 field_pos;
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index bc3f7dce42ba..eff5f4e380ac 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -28,6 +28,13 @@ is_affected_midr_range(const struct arm64_cpu_capabilities *entry, int scope)
> return is_midr_in_range(read_cpuid_id(), &entry->midr_range);
> }
>
> +static bool __maybe_unused
> +is_affected_midr_range_list(const struct arm64_cpu_capabilities *entry, int scope)
> +{
> + WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
> + return is_midr_in_range_list(read_cpuid_id(), entry->midr_range_list);
> +}
> +
> static bool __maybe_unused
> is_kryo_midr(const struct arm64_cpu_capabilities *entry, int scope)
> {
> @@ -184,6 +191,10 @@ static void qcom_enable_link_stack_sanitization(
> .type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM, \
> CAP_MIDR_RANGE(model, v_min, r_min, v_max, r_max)
>
> +#define CAP_MIDR_RANGE_LIST(list) \
> + .matches = is_affected_midr_range_list, \
> + .midr_range_list = list
> +
> /* Errata affecting a range of revisions of given model variant */
> #define ERRATA_MIDR_REV_RANGE(m, var, r_min, r_max) \
> ERRATA_MIDR_RANGE(m, var, r_min, var, r_max)
> @@ -197,6 +208,29 @@ static void qcom_enable_link_stack_sanitization(
> .type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM, \
> CAP_MIDR_ALL_VERSIONS(model)
>
> +/* Errata affecting a list of midr ranges, with same work around */
> +#define ERRATA_MIDR_RANGE_LIST(midr_list) \
> + .type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM, \
> + CAP_MIDR_RANGE_LIST(midr_list)
> +
> +#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
> +
> +/*
> + * List of CPUs where we need to issue a psci call to
> + * harden the branch predictor.
> + */
> +static const struct midr_range arm64_bp_harden_psci_cpus[] = {
> + MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
> + MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
> + MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
> + MIDR_ALL_VERSIONS(MIDR_CORTEX_A75),
> + MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
> + MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
> + {},
> +};
> +
> +#endif
> +
> const struct arm64_cpu_capabilities arm64_errata[] = {
> #if defined(CONFIG_ARM64_ERRATUM_826319) || \
> defined(CONFIG_ARM64_ERRATUM_827319) || \
> @@ -331,22 +365,7 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
> #ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
> {
> .capability = ARM64_HARDEN_BRANCH_PREDICTOR,
> - ERRATA_MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
> - .cpu_enable = enable_psci_bp_hardening,
> - },
> - {
> - .capability = ARM64_HARDEN_BRANCH_PREDICTOR,
> - ERRATA_MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
> - .cpu_enable = enable_psci_bp_hardening,
> - },
> - {
> - .capability = ARM64_HARDEN_BRANCH_PREDICTOR,
> - ERRATA_MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
> - .cpu_enable = enable_psci_bp_hardening,
> - },
> - {
> - .capability = ARM64_HARDEN_BRANCH_PREDICTOR,
> - ERRATA_MIDR_ALL_VERSIONS(MIDR_CORTEX_A75),
> + ERRATA_MIDR_RANGE_LIST(arm64_bp_harden_psci_cpus),
> .cpu_enable = enable_psci_bp_hardening,
> },
> {
> @@ -358,16 +377,6 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
> .capability = ARM64_HARDEN_BP_POST_GUEST_EXIT,
> ERRATA_MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR_V1),
> },
> - {
> - .capability = ARM64_HARDEN_BRANCH_PREDICTOR,
> - ERRATA_MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
> - .cpu_enable = enable_psci_bp_hardening,
> - },
> - {
> - .capability = ARM64_HARDEN_BRANCH_PREDICTOR,
> - ERRATA_MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
> - .cpu_enable = enable_psci_bp_hardening,
> - },
> #endif
> {
> }
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 247d34ea6b5e..65a8e5cc600c 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -864,6 +864,11 @@ 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)
> {
> + /* List of CPUs that are not vulnerable and don't need KPTI */
> + static const struct midr_range kpti_safe_list[] = {
> + MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
> + MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
> + };
>
> /* Forced on command line? */
> if (__kpti_forced) {
> @@ -877,11 +882,8 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
> return true;
>
> /* Don't force KPTI for CPUs that are not vulnerable */
> - switch (read_cpuid_id() & MIDR_CPU_MODEL_MASK) {
> - case MIDR_CAVIUM_THUNDERX2:
> - case MIDR_BRCM_VULCAN:
> + if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list))
> return false;
> - }
>
> /* Defer to CPU feature registers */
> return !has_cpuid_feature(entry, scope);
> --
> 2.14.3
>
>
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