[PATCH v2 03/12] KVM: arm64: Add ARM64_HAS_LPA2 CPU capability

[Ryan Roberts]

Expose FEAT_LPA2 as a capability so that we can take advantage of
alternatives patching in both the kernel and hypervisor.

Although FEAT_LPA2 presence is advertised separately for stage1 and
stage2, the expectation is that in practice both stages will either
support or not support it. Therefore we combine both into a single
capability, allowing us to simplify the implementation.

Signed-off-by: Ryan Roberts <ryan.roberts at arm.com>
---
 arch/arm64/include/asm/cpufeature.h |  5 ++++
 arch/arm64/kernel/cpufeature.c      | 40 +++++++++++++++++++++++++++++
 arch/arm64/tools/cpucaps            |  1 +
 3 files changed, 46 insertions(+)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 6bf013fb110d..59e4bf2341af 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -838,6 +838,11 @@ static inline bool system_supports_tlb_range(void)
 		cpus_have_const_cap(ARM64_HAS_TLB_RANGE);
 }
 
+static inline bool system_supports_lpa2(void)
+{
+	return cpus_have_const_cap(ARM64_HAS_LPA2);
+}
+
 int do_emulate_mrs(struct pt_regs *regs, u32 sys_reg, u32 rt);
 bool try_emulate_mrs(struct pt_regs *regs, u32 isn);
 
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 2e3e55139777..07b952e087bb 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1715,6 +1715,40 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 	return !meltdown_safe;
 }
 
+static inline bool has_lpa2_at_stage1(u64 mmfr0)
+{
+#if defined(CONFIG_ARM64_4K_PAGES) || defined(CONFIG_ARM64_16K_PAGES)
+	unsigned int tgran;
+
+	tgran = cpuid_feature_extract_unsigned_field(mmfr0,
+						ID_AA64MMFR0_EL1_TGRAN_SHIFT);
+	return tgran == ID_AA64MMFR0_EL1_TGRAN_LPA2;
+#else
+	return false;
+#endif
+}
+
+static inline bool has_lpa2_at_stage2(u64 mmfr0)
+{
+#if defined(CONFIG_ARM64_4K_PAGES) || defined(CONFIG_ARM64_16K_PAGES)
+	unsigned int tgran;
+
+	tgran = cpuid_feature_extract_unsigned_field(mmfr0,
+						ID_AA64MMFR0_EL1_TGRAN_2_SHIFT);
+	return tgran == ID_AA64MMFR0_EL1_TGRAN_2_SUPPORTED_LPA2;
+#else
+	return false;
+#endif
+}
+
+static bool has_lpa2(const struct arm64_cpu_capabilities *entry, int scope)
+{
+	u64 mmfr0;
+
+	mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
+	return has_lpa2_at_stage1(mmfr0) && has_lpa2_at_stage2(mmfr0);
+}
+
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 #define KPTI_NG_TEMP_VA		(-(1UL << PMD_SHIFT))
 
@@ -2772,6 +2806,12 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.matches = has_cpuid_feature,
 		.cpu_enable = cpu_enable_dit,
 	},
+	{
+		.desc = "Large Physical Address 2",
+		.capability = ARM64_HAS_LPA2,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_lpa2,
+	},
 	{},
 };
 
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 37b1340e9646..a9c5d453d473 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -32,6 +32,7 @@ HAS_GIC_CPUIF_SYSREGS
 HAS_GIC_PRIO_MASKING
 HAS_GIC_PRIO_RELAXED_SYNC
 HAS_LDAPR
+HAS_LPA2
 HAS_LSE_ATOMICS
 HAS_NESTED_VIRT
 HAS_NO_FPSIMD
-- 
2.25.1