kvm: nVMX: Check "load IA32_PAT" VM-exit control on vmentry

According to section "Checks on Host Control Registers and MSRs" in Intel
SDM vol 3C, the following check is performed on vmentry:

    If the "load IA32_PAT" VM-exit control is 1, the value of the field
    for the IA32_PAT MSR must be one that could be written by WRMSR
    without fault at CPL 0. Specifically, each of the 8 bytes in the
    field must have one of the values 0 (UC), 1 (WC), 4 (WT), 5 (WP),
    6 (WB), or 7 (UC-).
Signed-off-by: NKrish Sadhukhan <krish.sadhukhan@oracle.com>
Reviewed-by: NKarl Heubaum <karl.heubaum@oracle.com>
Suggested-by: NSean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: NSean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -2606,6 +2606,10 @@ static int nested_check_host_control_regs(struct kvm_vcpu *vcpu,
 	    is_noncanonical_address(vmcs12->host_ia32_sysenter_eip, vcpu))
 		return -EINVAL;
 
+	if ((vmcs12->vm_exit_controls & VM_EXIT_LOAD_IA32_PAT) &&
+	    !kvm_pat_valid(vmcs12->host_ia32_pat))
+		return -EINVAL;
+
 	/*
 	 * If the load IA32_EFER VM-exit control is 1, bits reserved in the
 	 * IA32_EFER MSR must be 0 in the field for that register. In addition,