x86/paravirt/xen: properly fill out the ldt ops

LTP testing showed that Xen does not properly implement
sys_modify_ldt().  This patch does the final little bits needed to
make the ldt work properly.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
index 3fee2aa..4895e06 100644
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -51,6 +51,8 @@
 	memset(newldt + oldsize * LDT_ENTRY_SIZE, 0,
 	       (mincount - oldsize) * LDT_ENTRY_SIZE);
 
+	paravirt_alloc_ldt(newldt, mincount);
+
 #ifdef CONFIG_X86_64
 	/* CHECKME: Do we really need this ? */
 	wmb();
@@ -75,6 +77,7 @@
 #endif
 	}
 	if (oldsize) {
+		paravirt_free_ldt(oldldt, oldsize);
 		if (oldsize * LDT_ENTRY_SIZE > PAGE_SIZE)
 			vfree(oldldt);
 		else
@@ -86,10 +89,13 @@
 static inline int copy_ldt(mm_context_t *new, mm_context_t *old)
 {
 	int err = alloc_ldt(new, old->size, 0);
+	int i;
 
 	if (err < 0)
 		return err;
-	memcpy(new->ldt, old->ldt, old->size * LDT_ENTRY_SIZE);
+
+	for(i = 0; i < old->size; i++)
+		write_ldt_entry(new->ldt, i, old->ldt + i * LDT_ENTRY_SIZE);
 	return 0;
 }
 
@@ -126,6 +132,7 @@
 		if (mm == current->active_mm)
 			clear_LDT();
 #endif
+		paravirt_free_ldt(mm->context.ldt, mm->context.size);
 		if (mm->context.size * LDT_ENTRY_SIZE > PAGE_SIZE)
 			vfree(mm->context.ldt);
 		else
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 94da4d5..d8f2277 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -348,6 +348,10 @@
 	.write_ldt_entry = native_write_ldt_entry,
 	.write_gdt_entry = native_write_gdt_entry,
 	.write_idt_entry = native_write_idt_entry,
+
+	.alloc_ldt = paravirt_nop,
+	.free_ldt = paravirt_nop,
+
 	.load_sp0 = native_load_sp0,
 
 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)