1 files changed, 87 insertions, 11 deletions

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index b4204fa743f0..053f6cbe928b 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2215,6 +2215,38 @@ static bool hvhe_possible(const struct arm64_cpu_capabilities *entry,
 	return arm64_test_sw_feature_override(ARM64_SW_FEATURE_OVERRIDE_HVHE);
 }
 
+static bool has_bbml2_noabort(const struct arm64_cpu_capabilities *caps, int scope)
+{
+	/*
+	 * We want to allow usage of BBML2 in as wide a range of kernel contexts
+	 * as possible. This list is therefore an allow-list of known-good
+	 * implementations that both support BBML2 and additionally, fulfill the
+	 * extra constraint of never generating TLB conflict aborts when using
+	 * the relaxed BBML2 semantics (such aborts make use of BBML2 in certain
+	 * kernel contexts difficult to prove safe against recursive aborts).
+	 *
+	 * Note that implementations can only be considered "known-good" if their
+	 * implementors attest to the fact that the implementation never raises
+	 * TLB conflict aborts for BBML2 mapping granularity changes.
+	 */
+	static const struct midr_range supports_bbml2_noabort_list[] = {
+		MIDR_REV_RANGE(MIDR_CORTEX_X4, 0, 3, 0xf),
+		MIDR_REV_RANGE(MIDR_NEOVERSE_V3, 0, 2, 0xf),
+		{}
+	};
+
+	/* Does our cpu guarantee to never raise TLB conflict aborts? */
+	if (!is_midr_in_range_list(supports_bbml2_noabort_list))
+		return false;
+
+	/*
+	 * We currently ignore the ID_AA64MMFR2_EL1 register, and only care
+	 * about whether the MIDR check passes.
+	 */
+
+	return true;
+}
+
 #ifdef CONFIG_ARM64_PAN
 static void cpu_enable_pan(const struct arm64_cpu_capabilities *__unused)
 {
@@ -2997,6 +3029,12 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		ARM64_CPUID_FIELDS(ID_AA64MMFR2_EL1, EVT, IMP)
 	},
 	{
+		.desc = "BBM Level 2 without TLB conflict abort",
+		.capability = ARM64_HAS_BBML2_NOABORT,
+		.type = ARM64_CPUCAP_EARLY_LOCAL_CPU_FEATURE,
+		.matches = has_bbml2_noabort,
+	},
+	{
 		.desc = "52-bit Virtual Addressing for KVM (LPA2)",
 		.capability = ARM64_HAS_LPA2,
 		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
@@ -3388,18 +3426,49 @@ static void update_cpu_capabilities(u16 scope_mask)
 
 	scope_mask &= ARM64_CPUCAP_SCOPE_MASK;
 	for (i = 0; i < ARM64_NCAPS; i++) {
+		bool match_all = false;
+		bool caps_set = false;
+		bool boot_cpu = false;
+
 		caps = cpucap_ptrs[i];
-		if (!caps || !(caps->type & scope_mask) ||
-		    cpus_have_cap(caps->capability) ||
-		    !caps->matches(caps, cpucap_default_scope(caps)))
+		if (!caps || !(caps->type & scope_mask))
+			continue;
+
+		match_all = cpucap_match_all_early_cpus(caps);
+		caps_set = cpus_have_cap(caps->capability);
+		boot_cpu = scope_mask & SCOPE_BOOT_CPU;
+
+		/*
+		 * Unless it's a match-all CPUs feature, avoid probing if
+		 * already detected.
+		 */
+		if (!match_all && caps_set)
 			continue;
 
-		if (caps->desc && !caps->cpus)
+		/*
+		 * A match-all CPUs capability is only set when probing the
+		 * boot CPU. It may be cleared subsequently if not detected on
+		 * secondary ones.
+		 */
+		if (match_all && !caps_set && !boot_cpu)
+			continue;
+
+		if (!caps->matches(caps, cpucap_default_scope(caps))) {
+			if (match_all)
+				__clear_bit(caps->capability, system_cpucaps);
+			continue;
+		}
+
+		/*
+		 * Match-all CPUs capabilities are logged later when the
+		 * system capabilities are finalised.
+		 */
+		if (!match_all && caps->desc && !caps->cpus)
 			pr_info("detected: %s\n", caps->desc);
 
 		__set_bit(caps->capability, system_cpucaps);
 
-		if ((scope_mask & SCOPE_BOOT_CPU) && (caps->type & SCOPE_BOOT_CPU))
+		if (boot_cpu && (caps->type & SCOPE_BOOT_CPU))
 			set_bit(caps->capability, boot_cpucaps);
 	}
 }
@@ -3800,17 +3869,24 @@ static void __init setup_system_capabilities(void)
 	enable_cpu_capabilities(SCOPE_ALL & ~SCOPE_BOOT_CPU);
 	apply_alternatives_all();
 
-	/*
-	 * Log any cpucaps with a cpumask as these aren't logged by
-	 * update_cpu_capabilities().
-	 */
 	for (int i = 0; i < ARM64_NCAPS; i++) {
 		const struct arm64_cpu_capabilities *caps = cpucap_ptrs[i];
 
-		if (caps && caps->cpus && caps->desc &&
-			cpumask_any(caps->cpus) < nr_cpu_ids)
+		if (!caps || !caps->desc)
+			continue;
+
+		/*
+		 * Log any cpucaps with a cpumask as these aren't logged by
+		 * update_cpu_capabilities().
+		 */
+		if (caps->cpus && cpumask_any(caps->cpus) < nr_cpu_ids)
 			pr_info("detected: %s on CPU%*pbl\n",
 				caps->desc, cpumask_pr_args(caps->cpus));
+
+		/* Log match-all CPUs capabilities */
+		if (cpucap_match_all_early_cpus(caps) &&
+		    cpus_have_cap(caps->capability))
+			pr_info("detected: %s\n", caps->desc);
 	}
 
 	/*