KVM: nVMX: WARN once and fail VM-Enter if eVMCS sees VMFUNC[63:32] != 0

WARN and reject nested VM-Enter if KVM is using eVMCS and manages to
allow a non-zero value in the upper 32 bits of VM-function controls.  The
eVMCS code assumes all inputs are 32-bit values and subtly drops the
upper bits.  WARN instead of adding proper "support", it's unlikely the
upper bits will be defined/used in the next decade.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220830133737.1539624-15-vkuznets@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
index c3a5309f6e828631407a07cd047efe1721cfe89c..b64e29f1359fc5d98ada0becf5daef5624cd1828 100644 (file)
--- a/arch/x86/kvm/vmx/evmcs.c
+++ b/arch/x86/kvm/vmx/evmcs.c
@@ -469,6 +469,14 @@ int nested_evmcs_check_controls(struct vmcs12 *vmcs12)
                                               vmcs12->vm_entry_controls)))
                return -EINVAL;
 
+       /*
+        * VM-Func controls are 64-bit, but KVM currently doesn't support any
+        * controls in bits 63:32, i.e. dropping those bits on the consistency
+        * check is intentional.
+        */
+       if (WARN_ON_ONCE(vmcs12->vm_function_control >> 32))
+               return -EINVAL;
+
        if (CC(!nested_evmcs_is_valid_controls(EVMCS_VMFUNC,
                                               vmcs12->vm_function_control)))
                return -EINVAL;