[PATCH v2 3/7] x86/kvm/hyper-v: Introduce nested_get_evmcs_version() helper

[Vitaly Kuznetsov <vkuznets@redhat.com>]

The upcoming KVM_GET_SUPPORTED_HV_CPUID ioctl will need to return
Enlightened VMCS version in HYPERV_CPUID_NESTED_FEATURES.EAX when
it was enabled.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/svm.c              |  7 +++++++
 arch/x86/kvm/vmx.c              | 24 +++++++++++++++++-------
 3 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e1a40e649cdc..184669d48d80 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1185,6 +1185,7 @@ struct kvm_x86_ops {
 
 	int (*nested_enable_evmcs)(struct kvm_vcpu *vcpu,
 				   uint16_t *vmcs_version);
+	uint16_t (*nested_get_evmcs_version)(struct kvm_vcpu *vcpu);
 };
 
 struct kvm_arch_async_pf {
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 0e21ccc46792..472f950ccab7 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7037,6 +7037,12 @@ static int svm_unregister_enc_region(struct kvm *kvm,
 	return ret;
 }
 
+static uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu)
+{
+	/* Not supported */
+	return 0;
+}
+
 static int nested_enable_evmcs(struct kvm_vcpu *vcpu,
 				   uint16_t *vmcs_version)
 {
@@ -7175,6 +7181,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 	.mem_enc_unreg_region = svm_unregister_enc_region,
 
 	.nested_enable_evmcs = nested_enable_evmcs,
+	.nested_get_evmcs_version = nested_get_evmcs_version,
 };
 
 static int __init svm_init(void)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4555077d69ce..f5d865e88095 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1605,6 +1605,21 @@ static inline void evmcs_sanitize_exec_ctrls(struct vmcs_config *vmcs_conf) {}
 static inline void evmcs_touch_msr_bitmap(void) {}
 #endif /* IS_ENABLED(CONFIG_HYPERV) */
 
+static uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	/*
+	 * vmcs_version represents the range of supported Enlightened VMCS
+	 * versions: lower 8 bits is the minimal version, higher 8 bits is the
+	 * maximum supported version. KVM supports versions from 1 to
+	 * KVM_EVMCS_VERSION.
+	 */
+	if (vmx->nested.enlightened_vmcs_enabled)
+		return (KVM_EVMCS_VERSION << 8) | 1;
+
+	return 0;
+}
+
 static int nested_enable_evmcs(struct kvm_vcpu *vcpu,
 			       uint16_t *vmcs_version)
 {
@@ -1616,14 +1631,8 @@ static int nested_enable_evmcs(struct kvm_vcpu *vcpu,
 
 	vmx->nested.enlightened_vmcs_enabled = true;
 
-	/*
-	 * vmcs_version represents the range of supported Enlightened VMCS
-	 * versions: lower 8 bits is the minimal version, higher 8 bits is the
-	 * maximum supported version. KVM supports versions from 1 to
-	 * KVM_EVMCS_VERSION.
-	 */
 	if (vmcs_version)
-		*vmcs_version = (KVM_EVMCS_VERSION << 8) | 1;
+		*vmcs_version = nested_get_evmcs_version(vcpu);
 
 	vmx->nested.msrs.pinbased_ctls_high &= ~EVMCS1_UNSUPPORTED_PINCTRL;
 	vmx->nested.msrs.entry_ctls_high &= ~EVMCS1_UNSUPPORTED_VMENTRY_CTRL;
@@ -15107,6 +15116,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
 	.enable_smi_window = enable_smi_window,
 
 	.nested_enable_evmcs = nested_enable_evmcs,
+	.nested_get_evmcs_version = nested_get_evmcs_version,
 };
 
 static void vmx_cleanup_l1d_flush(void)
-- 
2.19.2