x86: define a few selector values

TSS, LDT, and per-CPU entries all can benefit a little from also having
their selector values defined.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v2: New.

--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -761,7 +761,7 @@ void load_system_tables(void)
 	per_cpu(full_gdt_loaded, cpu) = false;
 	lgdt(&gdtr);
 	lidt(&idtr);
-	ltr(TSS_ENTRY << 3);
+	ltr(TSS_SELECTOR);
 	lldt(0);
 
 	enable_each_ist(idt_tables[cpu]);
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1572,7 +1572,7 @@ bool svm_load_segs(unsigned int ldt_ents
 
         _set_tssldt_desc(desc, ldt_base, ldt_ents * 8 - 1, SYS_DESC_ldt);
 
-        vmcb->ldtr.sel = LDT_ENTRY << 3;
+        vmcb->ldtr.sel = LDT_SELECTOR;
         vmcb->ldtr.attr = SYS_DESC_ldt | (_SEGMENT_P >> 8);
         vmcb->ldtr.limit = ldt_ents * 8 - 1;
         vmcb->ldtr.base = ldt_base;
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1128,7 +1128,7 @@ static int construct_vmcs(struct vcpu *v
     __vmwrite(HOST_GS_SELECTOR, 0);
     __vmwrite(HOST_FS_BASE, 0);
     __vmwrite(HOST_GS_BASE, 0);
-    __vmwrite(HOST_TR_SELECTOR, TSS_ENTRY << 3);
+    __vmwrite(HOST_TR_SELECTOR, TSS_SELECTOR);
 
     /* Host control registers. */
     v->arch.hvm.vmx.host_cr0 = read_cr0() & ~X86_CR0_TS;
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1917,7 +1917,7 @@ void load_TR(void)
     /* Switch to non-compat GDT (which has B bit clear) to execute LTR. */
     asm volatile (
         "sgdt %0; lgdt %2; ltr %w1; lgdt %0"
-        : "=m" (old_gdt) : "rm" (TSS_ENTRY << 3), "m" (tss_gdt) : "memory" );
+        : "=m" (old_gdt) : "rm" (TSS_SELECTOR), "m" (tss_gdt) : "memory" );
 }
 
 static unsigned int calc_ler_msr(void)
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -251,7 +251,7 @@ void do_double_fault(struct cpu_user_reg
 
     console_force_unlock();
 
-    asm ( "lsll %1, %0" : "=r" (cpu) : "rm" (PER_CPU_GDT_ENTRY << 3) );
+    asm ( "lsll %1, %0" : "=r" (cpu) : "rm" (PER_CPU_GDT_SELECTOR) );
 
     /* Find information saved during fault and dump it to the console. */
     printk("*** DOUBLE FAULT ***\n");
--- a/xen/include/asm-x86/desc.h
+++ b/xen/include/asm-x86/desc.h
@@ -36,6 +36,10 @@
 #define LDT_ENTRY (TSS_ENTRY + 2)
 #define PER_CPU_GDT_ENTRY (LDT_ENTRY + 2)
 
+#define TSS_SELECTOR         (TSS_ENTRY << 3)
+#define LDT_SELECTOR         (LDT_ENTRY << 3)
+#define PER_CPU_GDT_SELECTOR (PER_CPU_GDT_ENTRY << 3)
+
 #ifndef __ASSEMBLY__
 
 #define GUEST_KERNEL_RPL(d) (is_pv_32bit_domain(d) ? 1 : 3)
--- a/xen/include/asm-x86/ldt.h
+++ b/xen/include/asm-x86/ldt.h
@@ -16,7 +16,7 @@ static inline void load_LDT(struct vcpu
         desc = (!is_pv_32bit_vcpu(v) ? this_cpu(gdt) : this_cpu(compat_gdt))
                + LDT_ENTRY - FIRST_RESERVED_GDT_ENTRY;
         _set_tssldt_desc(desc, LDT_VIRT_START(v), ents*8-1, SYS_DESC_ldt);
-        lldt(LDT_ENTRY << 3);
+        lldt(LDT_SELECTOR);
     }
 }