[PATCH v2 07/23] arm64: cpufeature: Read MPAMIDR_EL1 in __cpuinfo_store_cpu()

[Will Deacon <will@kernel.org>]

From: Fuad Tabba <fuad.tabba@linux.dev>

MPAMIDR_EL1 is the one ID register __cpuinfo_store_cpu() doesn't read.
Its read was deferred to init_cpu_features() and update_cpu_features()
because it traps on firmware that fails to enable MPAM. Only the
sanitised ID_AA64PFR0_EL1 and ID_AA64PFR1_EL1 carried the arm64.nompam
override for such firmware.

Store ID_AA64PFR0_EL1 through read_cpuid_with_overrides() as well. Then
read MPAMIDR_EL1 in __cpuinfo_store_cpu() again, beside GMID_EL1, gated
on this CPU's overridden ID_AA64PFR0_EL1 and ID_AA64PFR1_EL1. cpu_data
is then complete before init_cpu_features() runs.

Other readers of the stored ID_AA64PFR0_EL1 see the override too. With
arm64.no32bit_el0, __cpuinfo_store_cpu() no longer reads the AArch32 ID
registers. Adding allow_mismatched_32bit_el0 no longer enables 32-bit
EL0 either.

detect_ftr_has_mpam(), a system-wide test on the sanitised values,
stays for the ARM64_MPAM capability.

Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kernel/cpufeature.c | 10 +++-------
 arch/arm64/kernel/cpuinfo.c    | 11 ++++-------
 2 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 3161531ad401..9212f10c1d1a 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1248,10 +1248,8 @@ void __init init_cpu_features(struct cpuinfo_arm64 *info)
 		cpacr_restore(cpacr);
 	}
 
-	if (detect_ftr_has_mpam()) {
-		info->reg_mpamidr = read_cpuid(MPAMIDR_EL1);
+	if (id_aa64pfr0_mpam(info->reg_id_aa64pfr0) || id_aa64pfr1_mpamfrac(info->reg_id_aa64pfr1))
 		init_cpu_ftr_reg(SYS_MPAMIDR_EL1, info->reg_mpamidr);
-	}
 
 	if (IS_ENABLED(CONFIG_ARM64_MTE) && id_aa64pfr1_mte(info->reg_id_aa64pfr1))
 		init_cpu_ftr_reg(SYS_GMID_EL1, info->reg_gmid);
@@ -1504,11 +1502,9 @@ void update_cpu_features(int cpu,
 		cpacr_restore(cpacr);
 	}
 
-	if (detect_ftr_has_mpam()) {
-		info->reg_mpamidr = read_cpuid(MPAMIDR_EL1);
+	if (id_aa64pfr0_mpam(info->reg_id_aa64pfr0) || id_aa64pfr1_mpamfrac(info->reg_id_aa64pfr1))
 		taint |= check_update_ftr_reg(SYS_MPAMIDR_EL1, cpu,
-					info->reg_mpamidr, boot->reg_mpamidr);
-	}
+					      info->reg_mpamidr, boot->reg_mpamidr);
 
 	/*
 	 * The kernel uses the LDGM/STGM instructions and the number of tags
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index d48167fe4218..0ae40b0c7b2f 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -495,7 +495,7 @@ static void __cpuinfo_store_cpu(struct cpuinfo_arm64 *info)
 	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_aa64pfr0 = read_cpuid_with_overrides(ID_AA64PFR0_EL1);
 	info->reg_id_aa64pfr1 = read_cpuid_with_overrides(ID_AA64PFR1_EL1);
 	info->reg_id_aa64pfr2 = read_cpuid(ID_AA64PFR2_EL1);
 	info->reg_id_aa64zfr0 = read_cpuid(ID_AA64ZFR0_EL1);
@@ -505,15 +505,12 @@ static void __cpuinfo_store_cpu(struct cpuinfo_arm64 *info)
 	if (IS_ENABLED(CONFIG_ARM64_MTE) && id_aa64pfr1_mte(info->reg_id_aa64pfr1))
 		info->reg_gmid = read_cpuid(GMID_EL1);
 
+	if (id_aa64pfr0_mpam(info->reg_id_aa64pfr0) || id_aa64pfr1_mpamfrac(info->reg_id_aa64pfr1))
+		info->reg_mpamidr = read_cpuid(MPAMIDR_EL1);
+
 	if (id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0))
 		__cpuinfo_store_cpu_32bit(&info->aarch32);
 
-	/*
-	 * info->reg_mpamidr deferred to {init,update}_cpu_features because we
-	 * don't want to read it (and trigger a trap on buggy firmware) if
-	 * using an aa64pfr0_el1 override to unconditionally disable MPAM.
-	 */
-
 	if (IS_ENABLED(CONFIG_ARM64_SME) &&
 	    id_aa64pfr1_sme(info->reg_id_aa64pfr1)) {
 		/*
-- 
2.56.0.385.gd3acb90ef8-goog