kvm: selftests: create a GDT and TSS

The GDT and the TSS base were left to zero, and this has interesting effects
when the TSS descriptor is later read to set up a VMCS's TR_BASE.  Basically
it worked by chance, and this patch fixes it by setting up all the protected
mode data structures properly.

Because the GDT and TSS addresses are virtual, the page tables now always
exist at the time of vcpu setup.

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

tools/testing/selftests/kvm/include/x86.h

@@ -59,8 +59,8 @@ enum x86_register {
 struct desc64 {
 	uint16_t limit0;
 	uint16_t base0;
-	unsigned base1:8, type:5, dpl:2, p:1;
-	unsigned limit1:4, zero0:3, g:1, base2:8;
+	unsigned base1:8, s:1, type:4, dpl:2, p:1;
+	unsigned limit1:4, avl:1, l:1, db:1, g:1, base2:8;
 	uint32_t base3;
 	uint32_t zero1;
 } __attribute__((packed));