Subject: [PATCH v2 02/94] arm64: Add ARM64_HAS_NESTED_VIRT cpufeature

From: Marc Zyngier <[email-masked]>
Date: Tue, 11 Feb 2020 17:48:06 +0000

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              |  3 ++-
 arch/arm64/include/asm/sysreg.h               |  1 +
 arch/arm64/kernel/cpufeature.c                | 26 +++++++++++++++++++
 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index dbc22d684627..cb61ace641f1 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2151,6 +2151,10 @@
 			[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-intel.ept=	[KVM,Intel] Disable extended page tables
 			(virtualized MMU) support on capable Intel chips.
 			Default is 1 (enabled)
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 865e0253fc1e..21f0067d8d40 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -58,7 +58,8 @@
 #define ARM64_WORKAROUND_SPECULATIVE_AT_NVHE	48
 #define ARM64_HAS_E0PD				49
 #define ARM64_HAS_RNG				50
+#define ARM64_HAS_NESTED_VIRT			51
 
-#define ARM64_NCAPS				51
+#define ARM64_NCAPS				52
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index b91570ff9db1..00b283d6d31a 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -687,6 +687,7 @@
 #define ID_AA64MMFR2_E0PD_SHIFT		60
 #define ID_AA64MMFR2_FWB_SHIFT		40
 #define ID_AA64MMFR2_AT_SHIFT		32
+#define ID_AA64MMFR2_NV_SHIFT		24
 #define ID_AA64MMFR2_LVA_SHIFT		16
 #define ID_AA64MMFR2_IESB_SHIFT		12
 #define ID_AA64MMFR2_LSM_SHIFT		8
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 0b6715625cf6..f0e58450eb16 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -243,6 +243,7 @@ static const struct arm64_ftr_bits ftr_id_aa64mmfr2[] = {
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_E0PD_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_FWB_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_AT_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_NV_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_LVA_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_IESB_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_LSM_SHIFT, 4, 0),
@@ -1241,6 +1242,21 @@ static void cpu_copy_el2regs(const struct arm64_cpu_capabilities *__unused)
 	if (!alternative_is_applied(ARM64_HAS_VIRT_HOST_EXTN))
 		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);
 #endif
 
 static void cpu_has_fwb(const struct arm64_cpu_capabilities *__unused)
@@ -1419,6 +1435,16 @@ 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,
+	},
 #endif	/* CONFIG_ARM64_VHE */
 	{
 		.desc = "32-bit EL0 Support",
-- 
2.20.1

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