KVM: nVMX: Allow VMREAD when Enlightened VMCS is in use
Hyper-V TLFS explicitly forbids VMREAD and VMWRITE instructions when
Enlightened VMCS interface is in use:
"Any VMREAD or VMWRITE instructions while an enlightened VMCS is
active is unsupported and can result in unexpected behavior.""
Windows 11 + WSL2 seems to ignore this, attempts to VMREAD VMCS field
0x4404 ("VM-exit interruption information") are observed. Failing
these attempts with nested_vmx_failInvalid() makes such guests
unbootable.
Microsoft confirms this is a Hyper-V bug and claims that it'll get fixed
eventually but for the time being we need a workaround. (Temporary) allow
VMREAD to get data from the currently loaded Enlightened VMCS.
Note: VMWRITE instructions remain forbidden, it is not clear how to
handle them properly and hopefully won't ever be needed.
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20220112170134.1904308-6-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/vmx/evmcs.h b/arch/x86/kvm/vmx/evmcs.h
index 9bc2521..8d70f9a 100644
--- a/arch/x86/kvm/vmx/evmcs.h
+++ b/arch/x86/kvm/vmx/evmcs.h
@@ -98,6 +98,18 @@ static __always_inline int evmcs_field_offset(unsigned long field,
return evmcs_field->offset;
}
+static inline u64 evmcs_read_any(struct hv_enlightened_vmcs *evmcs,
+ unsigned long field, u16 offset)
+{
+ /*
+ * vmcs12_read_any() doesn't care whether the supplied structure
+ * is 'struct vmcs12' or 'struct hv_enlightened_vmcs' as it takes
+ * the exact offset of the required field, use it for convenience
+ * here.
+ */
+ return vmcs12_read_any((void *)evmcs, field, offset);
+}
+
#if IS_ENABLED(CONFIG_HYPERV)
static __always_inline int get_evmcs_offset(unsigned long field,