KVM: x86: raise TSS exception for NULL CS and SS segments

Windows 2003 uses task switch to triple fault and reboot (the other
exception being reserved pdptrs bits).

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8d860e0301a0b00d926388195d8505edc0a8e212..2793186779110fe366b16064f2c6fa5492f2bdfa 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4410,6 +4410,15 @@ static int is_vm86_segment(struct kvm_vcpu *vcpu, int seg)
                (kvm_get_rflags(vcpu) & X86_EFLAGS_VM);
 }
 
+static void kvm_check_segment_descriptor(struct kvm_vcpu *vcpu, int seg,
+                                        u16 selector)
+{
+       /* NULL selector is not valid for CS and SS */
+       if (seg == VCPU_SREG_CS || seg == VCPU_SREG_SS)
+               if (!selector)
+                       kvm_queue_exception_e(vcpu, TS_VECTOR, selector >> 3);
+}
+
 int kvm_load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector,
                                int type_bits, int seg)
 {
@@ -4419,6 +4428,8 @@ int kvm_load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector,
                return kvm_load_realmode_segment(vcpu, selector, seg);
        if (load_segment_descriptor_to_kvm_desct(vcpu, selector, &kvm_seg))
                return 1;
+
+       kvm_check_segment_descriptor(vcpu, seg, selector);
        kvm_seg.type |= type_bits;
 
        if (seg != VCPU_SREG_SS && seg != VCPU_SREG_CS &&