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arm64: Add ARM64_HAS_NESTED_VIRT cpufeature

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Add a new ARM64_HAS_NESTED_VIRT feature to indicate that the
CPU has the ARMv8.3 nested virtualization capability, together
with the 'kvm-arm.mode=nested' command line option.

This will be used to support nested virtualization in KVM.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
[maz: moved the command-line option to kvm-arm.mode]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230209175820.1939006-2-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Jintack Lim 2023-02-09 17:58:03 +00:00 committed by Oliver Upton
parent 5dc4c995db
commit 675cabc899
5 changed files with 42 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
Documentation/admin-guide/kernel-parameters.txt
View File

@ -2553,9 +2553,14 @@
protected: nVHE-based mode with support for guests whose
state is kept private from the host.
nested: VHE-based mode with support for nested
virtualization. Requires at least ARMv8.3
hardware.
Defaults to VHE/nVHE based on hardware support. Setting
mode to "protected" will disable kexec and hibernation
for the host.
for the host. "nested" is experimental and should be
used with extreme caution.
kvm-arm.vgic_v3_group0_trap=
[KVM,ARM] Trap guest accesses to GICv3 group-0

5
arch/arm64/include/asm/kvm_host.h
View File

@ -60,9 +60,14 @@
enum kvm_mode {
KVM_MODE_DEFAULT,
KVM_MODE_PROTECTED,
KVM_MODE_NV,
KVM_MODE_NONE,
};
#ifdef CONFIG_KVM
enum kvm_mode kvm_get_mode(void);
#else
static inline enum kvm_mode kvm_get_mode(void) { return KVM_MODE_NONE; };
#endif
DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);

25
arch/arm64/kernel/cpufeature.c
View File

@ -1956,6 +1956,20 @@ static void cpu_copy_el2regs(const struct arm64_cpu_capabilities *__unused)
write_sysreg(read_sysreg(tpidr_el1), tpidr_el2);
}
static bool has_nested_virt_support(const struct arm64_cpu_capabilities *cap,
int scope)
{
if (kvm_get_mode() != KVM_MODE_NV)
return false;
if (!has_cpuid_feature(cap, scope)) {
pr_warn("unavailable: %s\n", cap->desc);
return false;
}
return true;
}
#ifdef CONFIG_ARM64_PAN
static void cpu_enable_pan(const struct arm64_cpu_capabilities *__unused)
{
@ -2215,6 +2229,17 @@ 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_EL1_NV_SHIFT,
.field_width = 4,
.min_field_value = ID_AA64MMFR2_EL1_NV_IMP,
},
{
.capability = ARM64_HAS_32BIT_EL0_DO_NOT_USE,
.type = ARM64_CPUCAP_SYSTEM_FEATURE,

5
arch/arm64/kvm/arm.c
View File

@ -2310,6 +2310,11 @@ static int __init early_kvm_mode_cfg(char *arg)
return 0;
}
if (strcmp(arg, "nested") == 0 && !WARN_ON(!is_kernel_in_hyp_mode())) {
kvm_mode = KVM_MODE_NV;
return 0;
}
return -EINVAL;
}
early_param("kvm-arm.mode", early_kvm_mode_cfg);

1
arch/arm64/tools/cpucaps
View File

@ -31,6 +31,7 @@ HAS_GENERIC_AUTH_IMP_DEF
HAS_IRQ_PRIO_MASKING
HAS_LDAPR
HAS_LSE_ATOMICS
HAS_NESTED_VIRT
HAS_NO_FPSIMD
HAS_NO_HW_PREFETCH
HAS_PAN