1 files changed, 33 insertions, 7 deletions

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 49352fad7d1d..bbbfdd495ebd 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -101,6 +101,17 @@ struct tls_descs {
 	struct desc_struct desc[3];
 };
 
+DEFINE_PER_CPU(enum xen_lazy_mode, xen_lazy_mode) = XEN_LAZY_NONE;
+DEFINE_PER_CPU(unsigned int, xen_lazy_nesting);
+
+enum xen_lazy_mode xen_get_lazy_mode(void)
+{
+	if (in_interrupt())
+		return XEN_LAZY_NONE;
+
+	return this_cpu_read(xen_lazy_mode);
+}
+
 /*
  * Updating the 3 TLS descriptors in the GDT on every task switch is
  * surprisingly expensive so we avoid updating them if they haven't
@@ -362,10 +373,25 @@ static noinstr unsigned long xen_get_debugreg(int reg)
 	return HYPERVISOR_get_debugreg(reg);
 }
 
+static void xen_start_context_switch(struct task_struct *prev)
+{
+	BUG_ON(preemptible());
+
+	if (this_cpu_read(xen_lazy_mode) == XEN_LAZY_MMU) {
+		arch_leave_lazy_mmu_mode();
+		set_ti_thread_flag(task_thread_info(prev), TIF_LAZY_MMU_UPDATES);
+	}
+	enter_lazy(XEN_LAZY_CPU);
+}
+
 static void xen_end_context_switch(struct task_struct *next)
 {
+	BUG_ON(preemptible());
+
 	xen_mc_flush();
-	paravirt_end_context_switch(next);
+	leave_lazy(XEN_LAZY_CPU);
+	if (test_and_clear_ti_thread_flag(task_thread_info(next), TIF_LAZY_MMU_UPDATES))
+		arch_enter_lazy_mmu_mode();
 }
 
 static unsigned long xen_store_tr(void)
@@ -472,7 +498,7 @@ static void xen_set_ldt(const void *addr, unsigned entries)
 
 	MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);
 
-	xen_mc_issue(PARAVIRT_LAZY_CPU);
+	xen_mc_issue(XEN_LAZY_CPU);
 }
 
 static void xen_load_gdt(const struct desc_ptr *dtr)
@@ -568,7 +594,7 @@ static void xen_load_tls(struct thread_struct *t, unsigned int cpu)
 	 * exception between the new %fs descriptor being loaded and
 	 * %fs being effectively cleared at __switch_to().
 	 */
-	if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_CPU)
+	if (xen_get_lazy_mode() == XEN_LAZY_CPU)
 		loadsegment(fs, 0);
 
 	xen_mc_batch();
@@ -577,7 +603,7 @@ static void xen_load_tls(struct thread_struct *t, unsigned int cpu)
 	load_TLS_descriptor(t, cpu, 1);
 	load_TLS_descriptor(t, cpu, 2);
 
-	xen_mc_issue(PARAVIRT_LAZY_CPU);
+	xen_mc_issue(XEN_LAZY_CPU);
 }
 
 static void xen_load_gs_index(unsigned int idx)
@@ -909,7 +935,7 @@ static void xen_load_sp0(unsigned long sp0)
 
 	mcs = xen_mc_entry(0);
 	MULTI_stack_switch(mcs.mc, __KERNEL_DS, sp0);
-	xen_mc_issue(PARAVIRT_LAZY_CPU);
+	xen_mc_issue(XEN_LAZY_CPU);
 	this_cpu_write(cpu_tss_rw.x86_tss.sp0, sp0);
 }
 
@@ -973,7 +999,7 @@ static void xen_write_cr0(unsigned long cr0)
 
 	MULTI_fpu_taskswitch(mcs.mc, (cr0 & X86_CR0_TS) != 0);
 
-	xen_mc_issue(PARAVIRT_LAZY_CPU);
+	xen_mc_issue(XEN_LAZY_CPU);
 }
 
 static void xen_write_cr4(unsigned long cr4)
@@ -1156,7 +1182,7 @@ static const typeof(pv_ops) xen_cpu_ops __initconst = {
 #endif
 		.io_delay = xen_io_delay,
 
-		.start_context_switch = paravirt_start_context_switch,
+		.start_context_switch = xen_start_context_switch,
 		.end_context_switch = xen_end_context_switch,
 	},
 };