x86/kvm/hyper-v: move VMX controls sanitization out of nested_enable_evmcs()

With fine grained VMX feature enablement QEMU>=4.2 tries to do KVM_SET_MSRS
with default (matching CPU model) values and in case eVMCS is also enabled,
fails.

It would be possible to drop VMX feature filtering completely and make
this a guest's responsibility: if it decides to use eVMCS it should know
which fields are available and which are not. Hyper-V mostly complies to
this, however, there are some problematic controls:
SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES
VM_{ENTRY,EXIT}_LOAD_IA32_PERF_GLOBAL_CTRL

which Hyper-V enables. As there are no corresponding fields in eVMCS, we
can't handle this properly in KVM. This is a Hyper-V issue.

Move VMX controls sanitization from nested_enable_evmcs() to vmx_get_msr(),
and do the bare minimum (only clear controls which are known to cause issues).
This allows userspace to keep setting controls it wants and at the same
time hides them from the guest.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 26 insertions, 6 deletions

diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
index 89c3e0caf39f..ba886fb7bc39 100644
--- a/arch/x86/kvm/vmx/evmcs.c
+++ b/arch/x86/kvm/vmx/evmcs.c
@@ -346,6 +346,32 @@ uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu)
        return 0;
 }
 
+void nested_evmcs_filter_control_msr(u32 msr_index, u64 *pdata)
+{
+	u32 ctl_low = (u32)*pdata;
+	u32 ctl_high = (u32)(*pdata >> 32);
+
+	/*
+	 * Hyper-V 2016 and 2019 try using these features even when eVMCS
+	 * is enabled but there are no corresponding fields.
+	 */
+	switch (msr_index) {
+	case MSR_IA32_VMX_EXIT_CTLS:
+	case MSR_IA32_VMX_TRUE_EXIT_CTLS:
+		ctl_high &= ~VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
+		break;
+	case MSR_IA32_VMX_ENTRY_CTLS:
+	case MSR_IA32_VMX_TRUE_ENTRY_CTLS:
+		ctl_high &= ~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
+		break;
+	case MSR_IA32_VMX_PROCBASED_CTLS2:
+		ctl_high &= ~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
+		break;
+	}
+
+	*pdata = ctl_low | ((u64)ctl_high << 32);
+}
+
 int nested_enable_evmcs(struct kvm_vcpu *vcpu,
 			uint16_t *vmcs_version)
 {
@@ -356,11 +382,5 @@ int nested_enable_evmcs(struct kvm_vcpu *vcpu,
 	if (vmcs_version)
 		*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;
-	vmx->nested.msrs.exit_ctls_high &= ~EVMCS1_UNSUPPORTED_VMEXIT_CTRL;
-	vmx->nested.msrs.secondary_ctls_high &= ~EVMCS1_UNSUPPORTED_2NDEXEC;
-	vmx->nested.msrs.vmfunc_controls &= ~EVMCS1_UNSUPPORTED_VMFUNC;
-
 	return 0;
 }