linux-kernel - [PATCH v2 02/11] arm64: cpufeature: detect FEAT

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Message-Id: <20230509142235.3284028-3-kristina.martsenko@arm.com>
Date:   Tue,  9 May 2023 15:22:26 +0100
From:   Kristina Martsenko <kristina.martsenko@....com>
To:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        Mark Brown <broonie@...nel.org>,
        Luis Machado <luis.machado@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 02/11] arm64: cpufeature: detect FEAT_HCX

Detect if the system has the new HCRX_EL2 register added in ARMv8.7/9.2,
so that subsequent patches can check for its presence.

KVM currently relies on the register being present on all CPUs (or
none), so the kernel will panic if that is not the case. Fortunately no
such systems currently exist, but this can be revisited if they appear.
Note that the kernel will not panic if CONFIG_KVM is disabled.

Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@....com>
---
 arch/arm64/kernel/cpufeature.c | 8 ++++++++
 arch/arm64/tools/cpucaps       | 1 +
 2 files changed, 9 insertions(+)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 7d7128c65161..9898ad77b1db 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -364,6 +364,7 @@ static const struct arm64_ftr_bits ftr_id_aa64mmfr0[] = {
 static const struct arm64_ftr_bits ftr_id_aa64mmfr1[] = {
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_EL1_TIDCP1_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_EL1_AFP_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_EL1_HCX_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_EL1_ETS_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_EL1_TWED_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR1_EL1_XNX_SHIFT, 4, 0),
@@ -2309,6 +2310,13 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
 		.matches = is_kvm_protected_mode,
 	},
+	{
+		.desc = "HCRX_EL2 register",
+		.capability = ARM64_HAS_HCX,
+		.type = ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE,
+		.matches = has_cpuid_feature,
+		ARM64_CPUID_FIELDS(ID_AA64MMFR1_EL1, HCX, IMP)
+	},
 #endif
 	{
 		.desc = "Kernel page table isolation (KPTI)",
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 40ba95472594..e1de10fa080e 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -32,6 +32,7 @@ HAS_GENERIC_AUTH_IMP_DEF
 HAS_GIC_CPUIF_SYSREGS
 HAS_GIC_PRIO_MASKING
 HAS_GIC_PRIO_RELAXED_SYNC
+HAS_HCX
 HAS_LDAPR
 HAS_LSE_ATOMICS
 HAS_NESTED_VIRT
-- 
2.25.1