[PATCH kvmtool v7 4/6] arm64: Add FEAT_E2H0 support

[Andre Przywara <andre.przywara@arm.com>]

From: Marc Zyngier <maz@kernel.org>

The --nested option allows a guest to boot at EL2 without FEAT_E2H0
(i.e. mandating VHE support). While this is great for "modern" operating
systems and hypervisors, a few legacy guests are stuck in a distant past.

To support those, add the --e2h0 command line option, that exposes
FEAT_E2H0 to the guest, at the expense of a number of other features, such
as FEAT_NV2. This is conditioned on the host itself supporting FEAT_E2H0.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Sascha Bischoff <sascha.bischoff@arm.com>
---
 arm64/include/kvm/kvm-config-arch.h | 5 ++++-
 arm64/kvm-cpu.c                     | 5 +++++
 arm64/kvm.c                         | 3 +++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arm64/include/kvm/kvm-config-arch.h b/arm64/include/kvm/kvm-config-arch.h
index 44c43367..73bf4211 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 42dc11da..5e4f3a7d 100644
--- a/arm64/kvm-cpu.c
+++ b/arm64/kvm-cpu.c
@@ -76,6 +76,11 @@ 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) {
+			if (!kvm__supports_extension(kvm, KVM_CAP_ARM_EL2_E2H0))
+				die("FEAT_E2H0 is not supported");
+			init->features[0] |= 1UL << KVM_ARM_VCPU_HAS_EL2_E2H0;
+		}
 	}
 }
 
diff --git a/arm64/kvm.c b/arm64/kvm.c
index 6e971dd7..4ce24933 100644
--- a/arm64/kvm.c
+++ b/arm64/kvm.c
@@ -440,6 +440,9 @@ void kvm__arch_validate_cfg(struct kvm *kvm)
 	    kvm->cfg.ram_addr + kvm->cfg.ram_size > SZ_4G) {
 		die("RAM extends above 4GB");
 	}
+
+	if (kvm->cfg.arch.e2h0 && !kvm->cfg.arch.nested_virt)
+		pr_warning("--e2h0 requires --nested, ignoring");
 }
 
 u64 kvm__arch_default_ram_address(void)
-- 
2.43.0