arm64: Check if GMID_EL1.BS is the same on all CPUs

The GMID_EL1.BS field determines the number of tags accessed by the
LDGM/STGM instructions (EL1 and up), used by the kernel for copying or
zeroing page tags.

Taint the kernel if GMID_EL1.BS differs between CPUs but only of
CONFIG_ARM64_MTE is enabled.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Suzuki K Poulose <Suzuki.Poulose@arm.com>
Link: https://lore.kernel.org/r/20210526193621.21559-3-catalin.marinas@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/include/asm/cpu.h b/arch/arm64/include/asm/cpu.h
index fe5a849..9088e72 100644 (file)
--- a/arch/arm64/include/asm/cpu.h
+++ b/arch/arm64/include/asm/cpu.h
@@ -20,6 +20,7 @@ struct cpuinfo_arm64 {
        u64             reg_dczid;
        u64             reg_midr;
        u64             reg_revidr;
+       u64             reg_gmid;
 
        u64             reg_id_aa64dfr0;
        u64             reg_id_aa64dfr1;

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 338840c..650de92 100644 (file)
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -619,6 +619,13 @@ static inline bool id_aa64pfr0_sve(u64 pfr0)
        return val > 0;
 }
 
+static inline bool id_aa64pfr1_mte(u64 pfr1)
+{
+       u32 val = cpuid_feature_extract_unsigned_field(pfr1, ID_AA64PFR1_MTE_SHIFT);
+
+       return val >= ID_AA64PFR1_MTE;
+}
+
 void __init setup_cpu_features(void);
 void check_local_cpu_capabilities(void);
 

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index efed283..0645300 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -400,6 +400,11 @@ static const struct arm64_ftr_bits ftr_dczid[] = {
        ARM64_FTR_END,
 };
 
+static const struct arm64_ftr_bits ftr_gmid[] = {
+       ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, SYS_GMID_EL1_BS_SHIFT, 4, 0),
+       ARM64_FTR_END,
+};
+
 static const struct arm64_ftr_bits ftr_id_isar0[] = {
        ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR0_DIVIDE_SHIFT, 4, 0),
        ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR0_DEBUG_SHIFT, 4, 0),
@@ -617,6 +622,9 @@ static const struct __ftr_reg_entry {
        /* Op1 = 0, CRn = 1, CRm = 2 */
        ARM64_FTR_REG(SYS_ZCR_EL1, ftr_zcr),
 
+       /* Op1 = 1, CRn = 0, CRm = 0 */
+       ARM64_FTR_REG(SYS_GMID_EL1, ftr_gmid),
+
        /* Op1 = 3, CRn = 0, CRm = 0 */
        { SYS_CTR_EL0, &arm64_ftr_reg_ctrel0 },
        ARM64_FTR_REG(SYS_DCZID_EL0, ftr_dczid),
@@ -911,6 +919,9 @@ void __init init_cpu_features(struct cpuinfo_arm64 *info)
                sve_init_vq_map();
        }
 
+       if (id_aa64pfr1_mte(info->reg_id_aa64pfr1))
+               init_cpu_ftr_reg(SYS_GMID_EL1, info->reg_gmid);
+
        /*
         * Initialize the indirect array of CPU hwcaps capabilities pointers
         * before we handle the boot CPU below.
@@ -1135,6 +1146,16 @@ void update_cpu_features(int cpu,
        }
 
        /*
+        * The kernel uses the LDGM/STGM instructions and the number of tags
+        * they read/write depends on the GMID_EL1.BS field. Check that the
+        * value is the same on all CPUs.
+        */
+       if (IS_ENABLED(CONFIG_ARM64_MTE) &&
+           id_aa64pfr1_mte(info->reg_id_aa64pfr1))
+               taint |= check_update_ftr_reg(SYS_GMID_EL1, cpu,
+                                             info->reg_gmid, boot->reg_gmid);
+
+       /*
         * This relies on a sanitised view of the AArch64 ID registers
         * (e.g. SYS_ID_AA64PFR0_EL1), so we call it last.
         */

diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 0e9e965..5321b82 100644 (file)
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -371,6 +371,9 @@ static void __cpuinfo_store_cpu(struct cpuinfo_arm64 *info)
        info->reg_id_aa64pfr1 = read_cpuid(ID_AA64PFR1_EL1);
        info->reg_id_aa64zfr0 = read_cpuid(ID_AA64ZFR0_EL1);
 
+       if (id_aa64pfr1_mte(info->reg_id_aa64pfr1))
+               info->reg_gmid = read_cpuid(GMID_EL1);
+
        /* Update the 32bit ID registers only if AArch32 is implemented */
        if (id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0)) {
                info->reg_id_dfr0 = read_cpuid(ID_DFR0_EL1);