KVM: selftests: Allocate x86's TSS at VM creation

Allocate x86's per-VM TSS at creation of a non-barebones VM.  Like the
GDT, the TSS is needed to actually run vCPUs, i.e. every non-barebones VM
is all but guaranteed to allocate the TSS sooner or later.

Reviewed-by: Ackerley Tng <ackerleytng@google.com>
Link: https://lore.kernel.org/r/20240314232637.2538648-16-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

tools/testing/selftests/kvm/lib/x86_64/processor.c

@@ -520,9 +520,6 @@ vm_paddr_t addr_arch_gva2gpa(struct kvm_vm *vm, vm_vaddr_t gva)
 static void kvm_setup_tss_64bit(struct kvm_vm *vm, struct kvm_segment *segp,
 				int selector)
 {
-	if (!vm->arch.tss)
-		vm->arch.tss = __vm_vaddr_alloc_page(vm, MEM_REGION_DATA);
-
 	memset(segp, 0, sizeof(*segp));
 	segp->base = vm->arch.tss;
 	segp->limit = 0x67;
@@ -620,6 +617,8 @@ static void vm_init_descriptor_tables(struct kvm_vm *vm)
 	vm->arch.gdt = __vm_vaddr_alloc_page(vm, MEM_REGION_DATA);
 	vm->arch.idt = __vm_vaddr_alloc_page(vm, MEM_REGION_DATA);
 	vm->handlers = __vm_vaddr_alloc_page(vm, MEM_REGION_DATA);
+	vm->arch.tss = __vm_vaddr_alloc_page(vm, MEM_REGION_DATA);
+
 	/* Handlers have the same address in both address spaces.*/
 	for (i = 0; i < NUM_INTERRUPTS; i++)
 		set_idt_entry(vm, i, (unsigned long)(&idt_handlers)[i], 0,