KVM: selftests: Add macro for TSS selector, rename up code/data macros

Add a proper #define for the TSS selector instead of open coding 0x18 and
hoping future developers don't use that selector for something else.

Opportunistically rename the code and data selector macros to shorten the
names, align the naming with the kernel's scheme, and capture that they
are *kernel* segments.

Reviewed-by: Ackerley Tng <ackerleytng@google.com>
Link: https://lore.kernel.org/r/20240314232637.2538648-17-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

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

@@ -15,8 +15,9 @@
 #define NUM_INTERRUPTS 256
 #endif
 
-#define DEFAULT_CODE_SELECTOR 0x8
-#define DEFAULT_DATA_SELECTOR 0x10
+#define KERNEL_CS	0x8
+#define KERNEL_DS	0x10
+#define KERNEL_TSS	0x18
 
 #define MAX_NR_CPUID_ENTRIES 100
 
@@ -548,11 +549,11 @@ static void vcpu_init_sregs(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
 	sregs.efer |= (EFER_LME | EFER_LMA | EFER_NX);
 
 	kvm_seg_set_unusable(&sregs.ldt);
-	kvm_seg_set_kernel_code_64bit(vm, DEFAULT_CODE_SELECTOR, &sregs.cs);
-	kvm_seg_set_kernel_data_64bit(vm, DEFAULT_DATA_SELECTOR, &sregs.ds);
-	kvm_seg_set_kernel_data_64bit(vm, DEFAULT_DATA_SELECTOR, &sregs.es);
-	kvm_seg_set_kernel_data_64bit(NULL, DEFAULT_DATA_SELECTOR, &sregs.gs);
-	kvm_setup_tss_64bit(vm, &sregs.tr, 0x18);
+	kvm_seg_set_kernel_code_64bit(vm, KERNEL_CS, &sregs.cs);
+	kvm_seg_set_kernel_data_64bit(vm, KERNEL_DS, &sregs.ds);
+	kvm_seg_set_kernel_data_64bit(vm, KERNEL_DS, &sregs.es);
+	kvm_seg_set_kernel_data_64bit(NULL, KERNEL_DS, &sregs.gs);
+	kvm_setup_tss_64bit(vm, &sregs.tr, KERNEL_TSS);
 
 	sregs.cr3 = vm->pgd;
 	vcpu_sregs_set(vcpu, &sregs);
@@ -621,8 +622,7 @@ static void vm_init_descriptor_tables(struct kvm_vm *vm)
 
 	/* 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,
-			DEFAULT_CODE_SELECTOR);
+		set_idt_entry(vm, i, (unsigned long)(&idt_handlers)[i], 0, KERNEL_CS);
 
 	*(vm_vaddr_t *)addr_gva2hva(vm, (vm_vaddr_t)(&exception_handlers)) = vm->handlers;
 }