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Date: Wed, 05 Aug 2015 15:58:51 +0100
From: "Suzuki K. Poulose" <Suzuki.Poulose@....com>
To: "linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
CC: Catalin Marinas <Catalin.Marinas@....com>,
Will Deacon <Will.Deacon@....com>,
Mark Rutland <Mark.Rutland@....com>,
"edward.nevill@...aro.org" <edward.nevill@...aro.org>,
"aph@...hat.com" <aph@...hat.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 05/10] arm64: Keep track of CPU feature registers
On 24/07/15 10:43, Suzuki K. Poulose wrote:
> From: "Suzuki K. Poulose" <suzuki.poulose@....com>
>
> This patch adds an infrastructure to keep track of the CPU feature
> registers on the system. This patch also consolidates the cpuinfo
> SANITY checks which ensures that we don't have conflicting feature
> supports across the CPUs.
>
> Each register has a set of feature bits defined by the architecture.
> We define the following attributes:
>
> 1) strict - If strict matching is required for the field across the
> all the CPUs for SANITY checks.
> 2) visible - If the field is exposed to the userspace (See documentation
> for more details).
>
> The default 'safe' value for the feature is also defined, which will be
> used:
> 1) To set the value for a 'discrete' feature with conflicting values.
> 2) To set the value for an 'invisible' feature for the userspace.
>
> The infrastructure keeps track of the following values for a feature
> register:
> - user visible value
> - system wide safe value
>
> Signed-off-by: Suzuki K. Poulose <suzuki.poulose@....com>
> ---
> arch/arm64/include/asm/cpu.h | 149 ++++++++++++++++
> arch/arm64/kernel/cpuinfo.c | 399 ++++++++++++++++++++++++++++++++++++++----
> 2 files changed, 511 insertions(+), 37 deletions(-)
>
> diff --git a/arch/arm64/include/asm/cpu.h b/arch/arm64/include/asm/cpu.h
> index a34de72..c7b0b89 100644
> --- a/arch/arm64/include/asm/cpu.h
> +++ b/arch/arm64/include/asm/cpu.h
...
> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
> index a13468b..ae2a37f 100644
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -31,6 +31,207 @@
> #include <linux/sched.h>
> #include <linux/smp.h>
>
...
> -#define CHECK_MASK(field, mask, boot, cur, cpu) \
> - check_reg_mask(#field, mask, (boot)->reg_ ## field, (cur)->reg_ ## field, cpu)
> -
> -#define CHECK(field, boot, cur, cpu) \
> - CHECK_MASK(field, ~0ULL, boot, cur, cpu)
> +#define CHECK_CPUINFO(field) \
> + ({ \
> + int __rc = 0; \
> + struct arm64_ftr_reg *__regp = get_arm64_sys_reg(sys_ ## field); \
> + if (__regp) { \
> + __rc = check_reg_mask(__regp, \
> + (boot)->reg_ ## field, \
> + (cur)->reg_ ## field, cpu); \
> + update_cpu_ftr_reg(__regp, cur->reg_ ## field, cpu); \
> + } \
> + __rc; \
> + })
>
> /*
> * Verify that CPUs don't have unexpected differences that will cause problems.
> @@ -123,17 +448,17 @@ static void cpuinfo_sanity_check(struct cpuinfo_arm64 *cur)
> * caches should look identical. Userspace JITs will make use of
> * *minLine.
> */
> - diff |= CHECK_MASK(ctr, 0xffff3fff, boot, cur, cpu);
> + diff |= CHECK_CPUINFO(ctr);
>
> /*
> * Userspace may perform DC ZVA instructions. Mismatched block sizes
> * could result in too much or too little memory being zeroed if a
> * process is preempted and migrated between CPUs.
> */
> - diff |= CHECK(dczid, boot, cur, cpu);
> + diff |= CHECK_CPUINFO(dczid);
>
> /* If different, timekeeping will be broken (especially with KVM) */
> - diff |= CHECK(cntfrq, boot, cur, cpu);
> + diff |= CHECK_CPUINFO(cntfrq);
>
> /*
> * The kernel uses self-hosted debug features and expects CPUs to
> @@ -141,15 +466,15 @@ static void cpuinfo_sanity_check(struct cpuinfo_arm64 *cur)
> * and BRPs to be identical.
> * ID_AA64DFR1 is currently RES0.
> */
> - diff |= CHECK(id_aa64dfr0, boot, cur, cpu);
> - diff |= CHECK(id_aa64dfr1, boot, cur, cpu);
> + diff |= CHECK_CPUINFO(id_aa64dfr0);
> + diff |= CHECK_CPUINFO(id_aa64dfr1);
>
> /*
> * Even in big.LITTLE, processors should be identical instruction-set
> * wise.
> */
> - diff |= CHECK(id_aa64isar0, boot, cur, cpu);
> - diff |= CHECK(id_aa64isar1, boot, cur, cpu);
> + diff |= CHECK_CPUINFO(id_aa64isar0);
> + diff |= CHECK_CPUINFO(id_aa64isar1);
>
> /*
> * Differing PARange support is fine as long as all peripherals and
> @@ -157,42 +482,42 @@ static void cpuinfo_sanity_check(struct cpuinfo_arm64 *cur)
> * Linux should not care about secure memory.
> * ID_AA64MMFR1 is currently RES0.
> */
> - diff |= CHECK_MASK(id_aa64mmfr0, 0xffffffffffff0ff0, boot, cur, cpu);
> - diff |= CHECK(id_aa64mmfr1, boot, cur, cpu);
> + diff |= CHECK_CPUINFO(id_aa64mmfr0);
> + diff |= CHECK_CPUINFO(id_aa64mmfr1);
>
> /*
> * EL3 is not our concern.
> * ID_AA64PFR1 is currently RES0.
> */
> - diff |= CHECK_MASK(id_aa64pfr0, 0xffffffffffff0fff, boot, cur, cpu);
> - diff |= CHECK(id_aa64pfr1, boot, cur, cpu);
> + diff |= CHECK_CPUINFO(id_aa64pfr0);
> + diff |= CHECK_CPUINFO(id_aa64pfr1);
>
> /*
> * If we have AArch32, we care about 32-bit features for compat. These
> * registers should be RES0 otherwise.
> */
> - diff |= CHECK(id_dfr0, boot, cur, cpu);
> - diff |= CHECK(id_isar0, boot, cur, cpu);
> - diff |= CHECK(id_isar1, boot, cur, cpu);
> - diff |= CHECK(id_isar2, boot, cur, cpu);
> - diff |= CHECK(id_isar3, boot, cur, cpu);
> - diff |= CHECK(id_isar4, boot, cur, cpu);
> - diff |= CHECK(id_isar5, boot, cur, cpu);
> + diff |= CHECK_CPUINFO(id_dfr0);
> + diff |= CHECK_CPUINFO(id_isar0);
> + diff |= CHECK_CPUINFO(id_isar1);
> + diff |= CHECK_CPUINFO(id_isar2);
> + diff |= CHECK_CPUINFO(id_isar3);
> + diff |= CHECK_CPUINFO(id_isar4);
> + diff |= CHECK_CPUINFO(id_isar5);
> /*
> * Regardless of the value of the AuxReg field, the AIFSR, ADFSR, and
> * ACTLR formats could differ across CPUs and therefore would have to
> * be trapped for virtualization anyway.
> */
> - diff |= CHECK_MASK(id_mmfr0, 0xff0fffff, boot, cur, cpu);
> - diff |= CHECK(id_mmfr1, boot, cur, cpu);
> - diff |= CHECK(id_mmfr2, boot, cur, cpu);
> - diff |= CHECK(id_mmfr3, boot, cur, cpu);
> - diff |= CHECK(id_pfr0, boot, cur, cpu);
> - diff |= CHECK(id_pfr1, boot, cur, cpu);
> + diff |= CHECK_CPUINFO(id_mmfr0);
> + diff |= CHECK_CPUINFO(id_mmfr1);
> + diff |= CHECK_CPUINFO(id_mmfr2);
> + diff |= CHECK_CPUINFO(id_mmfr3);
> + diff |= CHECK_CPUINFO(id_pfr0);
> + diff |= CHECK_CPUINFO(id_pfr1);
>
> - diff |= CHECK(mvfr0, boot, cur, cpu);
> - diff |= CHECK(mvfr1, boot, cur, cpu);
> - diff |= CHECK(mvfr2, boot, cur, cpu);
> + diff |= CHECK_CPUINFO(mvfr0);
> + diff |= CHECK_CPUINFO(mvfr1);
> + diff |= CHECK_CPUINFO(mvfr2);
>
> /*
> * Mismatched CPU features are a recipe for disaster. Don't even
> @@ -239,7 +564,7 @@ static void __cpuinfo_store_cpu(struct cpuinfo_arm64 *info)
> cpuinfo_detect_icache_policy(info);
>
> check_local_cpu_errata();
> - check_local_cpu_features();
> + cpuinfo_sanity_check(info);
These two changes shouldn't be there, I have fixed it locally.
> update_cpu_features(info);
> }
>
> @@ -247,13 +572,13 @@ void cpuinfo_store_cpu(void)
> {
> struct cpuinfo_arm64 *info = this_cpu_ptr(&cpu_data);
> __cpuinfo_store_cpu(info);
> - cpuinfo_sanity_check(info);
As above, this line should be retained here.
> }
>
> void __init cpuinfo_store_boot_cpu(void)
> {
> struct cpuinfo_arm64 *info = &per_cpu(cpu_data, 0);
> __cpuinfo_store_cpu(info);
> + init_cpu_ftrs(info);
Thanks
Suzuki
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