arm64: cpufeature: Add ID_AA64MMFR4_EL1 handling

Add ID_AA64MMFR4_EL1 to the list of idregs the kernel knows about,
and describe the E2H0 field.
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20240122181344.258974-6-maz@kernel.orgSigned-off-by: Oliver Upton <oliver.upton@linux.dev>

arch/arm64/include/asm/cpu.h

@@ -56,6 +56,7 @@ struct cpuinfo_arm64 {
 	u64		reg_id_aa64mmfr1;
 	u64		reg_id_aa64mmfr2;
 	u64		reg_id_aa64mmfr3;
+	u64		reg_id_aa64mmfr4;
 	u64		reg_id_aa64pfr0;
 	u64		reg_id_aa64pfr1;
 	u64		reg_id_aa64zfr0;

arch/arm64/kernel/cpufeature.c

@@ -437,6 +437,11 @@ static const struct arm64_ftr_bits ftr_id_aa64mmfr3[] = {
 	ARM64_FTR_END,
 };
 
+static const struct arm64_ftr_bits ftr_id_aa64mmfr4[] = {
+	S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR4_EL1_E2H0_SHIFT, 4, 0),
+	ARM64_FTR_END,
+};
+
 static const struct arm64_ftr_bits ftr_ctr[] = {
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_EXACT, 31, 1, 1), /* RES1 */
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, CTR_EL0_DIC_SHIFT, 1, 1),
@@ -754,6 +759,7 @@ static const struct __ftr_reg_entry {
 			       &id_aa64mmfr1_override),
 	ARM64_FTR_REG(SYS_ID_AA64MMFR2_EL1, ftr_id_aa64mmfr2),
 	ARM64_FTR_REG(SYS_ID_AA64MMFR3_EL1, ftr_id_aa64mmfr3),
+	ARM64_FTR_REG(SYS_ID_AA64MMFR4_EL1, ftr_id_aa64mmfr4),
 
 	/* Op1 = 1, CRn = 0, CRm = 0 */
 	ARM64_FTR_REG(SYS_GMID_EL1, ftr_gmid),
@@ -1078,6 +1084,7 @@ void __init init_cpu_features(struct cpuinfo_arm64 *info)
 	init_cpu_ftr_reg(SYS_ID_AA64MMFR1_EL1, info->reg_id_aa64mmfr1);
 	init_cpu_ftr_reg(SYS_ID_AA64MMFR2_EL1, info->reg_id_aa64mmfr2);
 	init_cpu_ftr_reg(SYS_ID_AA64MMFR3_EL1, info->reg_id_aa64mmfr3);
+	init_cpu_ftr_reg(SYS_ID_AA64MMFR4_EL1, info->reg_id_aa64mmfr4);
 	init_cpu_ftr_reg(SYS_ID_AA64PFR0_EL1, info->reg_id_aa64pfr0);
 	init_cpu_ftr_reg(SYS_ID_AA64PFR1_EL1, info->reg_id_aa64pfr1);
 	init_cpu_ftr_reg(SYS_ID_AA64ZFR0_EL1, info->reg_id_aa64zfr0);

arch/arm64/kernel/cpuinfo.c

@@ -447,6 +447,7 @@ static void __cpuinfo_store_cpu(struct cpuinfo_arm64 *info)
 	info->reg_id_aa64mmfr1 = read_cpuid(ID_AA64MMFR1_EL1);
 	info->reg_id_aa64mmfr2 = read_cpuid(ID_AA64MMFR2_EL1);
 	info->reg_id_aa64mmfr3 = read_cpuid(ID_AA64MMFR3_EL1);
+	info->reg_id_aa64mmfr4 = read_cpuid(ID_AA64MMFR4_EL1);
 	info->reg_id_aa64pfr0 = read_cpuid(ID_AA64PFR0_EL1);
 	info->reg_id_aa64pfr1 = read_cpuid(ID_AA64PFR1_EL1);
 	info->reg_id_aa64zfr0 = read_cpuid(ID_AA64ZFR0_EL1);