Subject: [PATCH v4 01/66] arm64: Add ARM64_HAS_NESTED_VIRT cpufeature

From: Marc Zyngier <[email-masked]>
Date: Mon, 10 May 2021 17:58:15 +0100

From: Jintack Lim <[email-masked]>

Add a new ARM64_HAS_NESTED_VIRT feature to indicate that the
CPU has the ARMv8.3 nested virtualization capability.

This will be used to support nested virtualization in KVM.

Signed-off-by: Jintack Lim <[email-masked]>
Signed-off-by: Andre Przywara <[email-masked]>
Signed-off-by: Christoffer Dall <[email-masked]>
Signed-off-by: Marc Zyngier <[email-masked]>
---
 .../admin-guide/kernel-parameters.txt         |  4 +++
 arch/arm64/include/asm/cpucaps.h              |  1 +
 arch/arm64/kernel/cpufeature.c                | 25 +++++++++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index cb89dbdedc46..78ca804a6754 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2320,6 +2320,10 @@
 			[KVM,ARM] Allow use of GICv4 for direct injection of
 			LPIs.
 
+	kvm-arm.nested=
+			[KVM,ARM] Allow nested virtualization in KVM/ARM.
+			Default is 0 (disabled)
+
 	kvm_cma_resv_ratio=n [PPC]
 			Reserves given percentage from system memory area for
 			contiguous memory allocation for KVM hash pagetable
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index b0c5eda0498f..8d0cf022010f 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -16,6 +16,7 @@
 #define ARM64_WORKAROUND_CAVIUM_23154		6
 #define ARM64_WORKAROUND_834220			7
 #define ARM64_HAS_NO_HW_PREFETCH		8
+#define ARM64_HAS_NESTED_VIRT			9
 #define ARM64_HAS_VIRT_HOST_EXTN		11
 #define ARM64_WORKAROUND_CAVIUM_27456		12
 #define ARM64_HAS_32BIT_EL0			13
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index efed2830d141..056de86d7f6f 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1645,6 +1645,21 @@ static void cpu_copy_el2regs(const struct arm64_cpu_capabilities *__unused)
 		write_sysreg(read_sysreg(tpidr_el1), tpidr_el2);
 }
 
+static bool nested_param;
+static bool has_nested_virt_support(const struct arm64_cpu_capabilities *cap,
+				    int scope)
+{
+	return has_cpuid_feature(cap, scope) &&
+		nested_param;
+}
+
+static int __init kvmarm_nested_cfg(char *buf)
+{
+	return strtobool(buf, &nested_param);
+}
+
+early_param("kvm-arm.nested", kvmarm_nested_cfg);
+
 static void cpu_has_fwb(const struct arm64_cpu_capabilities *__unused)
 {
 	u64 val = read_sysreg_s(SYS_CLIDR_EL1);
@@ -1865,6 +1880,16 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.matches = runs_at_el2,
 		.cpu_enable = cpu_copy_el2regs,
 	},
+	{
+		.desc = "Nested Virtualization Support",
+		.capability = ARM64_HAS_NESTED_VIRT,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_nested_virt_support,
+		.sys_reg = SYS_ID_AA64MMFR2_EL1,
+		.sign = FTR_UNSIGNED,
+		.field_pos = ID_AA64MMFR2_NV_SHIFT,
+		.min_field_value = 1,
+	},
 	{
 		.desc = "32-bit EL0 Support",
 		.capability = ARM64_HAS_32BIT_EL0,
-- 
2.29.2

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