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>

arch/x86/kernel/ldt.c

@@ -51,6 +51,8 @@ static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
 	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 @@ static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
 #endif
 	}
 	if (oldsize) {
+		paravirt_free_ldt(oldldt, oldsize);
 		if (oldsize * LDT_ENTRY_SIZE > PAGE_SIZE)
 			vfree(oldldt);
 		else
@@ -86,10 +89,13 @@ static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
 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 @@ void destroy_context(struct mm_struct *mm)
 		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

arch/x86/kernel/paravirt.c

@@ -348,6 +348,10 @@ struct pv_cpu_ops pv_cpu_ops = {
 	.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)

arch/x86/xen/enlighten.c

@@ -325,6 +325,26 @@ static unsigned long xen_store_tr(void)
 	return 0;
 }
 
+static void xen_alloc_ldt(struct desc_struct *ldt, unsigned entries)
+{
+	unsigned pages = roundup(entries * LDT_ENTRY_SIZE, PAGE_SIZE);
+	void *v = ldt;
+	int i;
+
+	for(i = 0; i < pages; i += PAGE_SIZE)
+		make_lowmem_page_readonly(v + i);
+}
+
+static void xen_free_ldt(struct desc_struct *ldt, unsigned entries)
+{
+	unsigned pages = roundup(entries * LDT_ENTRY_SIZE, PAGE_SIZE);
+	void *v = ldt;
+	int i;
+
+	for(i = 0; i < pages; i += PAGE_SIZE)
+		make_lowmem_page_readwrite(v + i);
+}
+
 static void xen_set_ldt(const void *addr, unsigned entries)
 {
 	struct mmuext_op *op;
@@ -1220,6 +1240,9 @@ static const struct pv_cpu_ops xen_cpu_ops __initdata = {
 	.load_gs_index = xen_load_gs_index,
 #endif
 
+	.alloc_ldt = xen_alloc_ldt,
+	.free_ldt = xen_free_ldt,
+
 	.store_gdt = native_store_gdt,
 	.store_idt = native_store_idt,
 	.store_tr = xen_store_tr,

include/asm-x86/desc.h

@@ -97,7 +97,15 @@ static inline int desc_empty(const void *ptr)
 	native_write_gdt_entry(dt, entry, desc, type)
 #define write_idt_entry(dt, entry, g)		\
 	native_write_idt_entry(dt, entry, g)
-#endif
+
+static inline void paravirt_alloc_ldt(struct desc_struct *ldt, unsigned entries)
+{
+}
+
+static inline void paravirt_free_ldt(struct desc_struct *ldt, unsigned entries)
+{
+}
+#endif	/* CONFIG_PARAVIRT */
 
 static inline void native_write_idt_entry(gate_desc *idt, int entry,
 					  const gate_desc *gate)

include/asm-x86/paravirt.h

@@ -124,6 +124,9 @@ struct pv_cpu_ops {
 				int entrynum, const void *desc, int size);
 	void (*write_idt_entry)(gate_desc *,
 				int entrynum, const gate_desc *gate);
+	void (*alloc_ldt)(struct desc_struct *ldt, unsigned entries);
+	void (*free_ldt)(struct desc_struct *ldt, unsigned entries);
+
 	void (*load_sp0)(struct tss_struct *tss, struct thread_struct *t);
 
 	void (*set_iopl_mask)(unsigned mask);
@@ -824,6 +827,16 @@ do {							\
 	(aux) = __aux;					\
 } while (0)
 
+static inline void paravirt_alloc_ldt(struct desc_struct *ldt, unsigned entries)
+{
+	PVOP_VCALL2(pv_cpu_ops.alloc_ldt, ldt, entries);
+}
+
+static inline void paravirt_free_ldt(struct desc_struct *ldt, unsigned entries)
+{
+	PVOP_VCALL2(pv_cpu_ops.free_ldt, ldt, entries);
+}
+
 static inline void load_TR_desc(void)
 {
 	PVOP_VCALL0(pv_cpu_ops.load_tr_desc);