From: Marc Zyngier <maz@xxxxxxxxxx>
To reduce code complexity, KVM only supports nested virtualisation in
VHE mode. So to allow recursive nested virtualisation, and be able to
expose FEAT_NV2 to a guest, we must prevent a guest from turning off
HCR_EL2.E2H, which is covered by not advertising the FEAT_E2H0 architecture
feature.
To allow people to run a guest in non-VHE mode, KVM introduced the
KVM_ARM_VCPU_HAS_EL2_E2H0 feature flag, which will allow control over
HCR_EL2.E2H, but at the cost of turning off FEAT_NV2.
Add a kvmtool command line option "--e2h0" to set that feature bit when
creating a guest, to gain non-VHE, but lose recursive nested virt.
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
arm64/include/kvm/kvm-config-arch.h | 5 ++++-
arm64/kvm-cpu.c | 2 ++
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/arm64/include/kvm/kvm-config-arch.h b/arm64/include/kvm/kvm-config-arch.h
index 44c43367b..73bf4211a 100644
--- a/arm64/include/kvm/kvm-config-arch.h
+++ b/arm64/include/kvm/kvm-config-arch.h
@@ -11,6 +11,7 @@ struct kvm_config_arch {
bool has_pmuv3;
bool mte_disabled;
bool nested_virt;
+ bool e2h0;
u64 kaslr_seed;
enum irqchip_type irqchip;
u64 fw_addr;
@@ -63,6 +64,8 @@ int sve_vl_parser(const struct option *opt, const char *arg, int unset);
OPT_U64('\0', "counter-offset", &(cfg)->counter_offset, \
"Specify the counter offset, defaulting to 0"), \
OPT_BOOLEAN('\0', "nested", &(cfg)->nested_virt, \
- "Start VCPUs in EL2 (for nested virt)"),
+ "Start VCPUs in EL2 (for nested virt)"), \
+ OPT_BOOLEAN('\0', "e2h0", &(cfg)->e2h0, \
+ "Create guest without VHE support"),
#endif /* ARM_COMMON__KVM_CONFIG_ARCH_H */
diff --git a/arm64/kvm-cpu.c b/arm64/kvm-cpu.c
index 42dc11dad..6eb76dff4 100644
--- a/arm64/kvm-cpu.c
+++ b/arm64/kvm-cpu.c
@@ -76,6 +76,8 @@ static void kvm_cpu__select_features(struct kvm *kvm, struct kvm_vcpu_init *init
if (!kvm__supports_extension(kvm, KVM_CAP_ARM_EL2))
die("EL2 (nested virt) is not supported");
init->features[0] |= 1UL << KVM_ARM_VCPU_HAS_EL2;
+ if (kvm->cfg.arch.e2h0)
+ init->features[0] |= 1UL << KVM_ARM_VCPU_HAS_EL2_E2H0;
}
}
--
2.25.1
