xen: yield to IPI target if necessary
When sending a call-function IPI to a vcpu, yield if the vcpu isn't
running.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 557b8e2..865953e 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -360,7 +360,8 @@
void *info, int wait)
{
struct call_data_struct data;
- int cpus;
+ int cpus, cpu;
+ bool yield;
/* Holding any lock stops cpus from going down. */
spin_lock(&call_lock);
@@ -389,9 +390,14 @@
/* Send a message to other CPUs and wait for them to respond */
xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);
- /* Make sure other vcpus get a chance to run.
- XXX too severe? Maybe we should check the other CPU's states? */
- HYPERVISOR_sched_op(SCHEDOP_yield, 0);
+ /* Make sure other vcpus get a chance to run if they need to. */
+ yield = false;
+ for_each_cpu_mask(cpu, mask)
+ if (xen_vcpu_stolen(cpu))
+ yield = true;
+
+ if (yield)
+ HYPERVISOR_sched_op(SCHEDOP_yield, 0);
/* Wait for response */
while (atomic_read(&data.started) != cpus ||
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index dfd6db6..d083ff5 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -105,6 +105,12 @@
} while (get64(&state->state_entry_time) != state_time);
}
+/* return true when a vcpu could run but has no real cpu to run on */
+bool xen_vcpu_stolen(int vcpu)
+{
+ return per_cpu(runstate, vcpu).state == RUNSTATE_runnable;
+}
+
static void setup_runstate_info(int cpu)
{
struct vcpu_register_runstate_memory_area area;
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index b5697ba..3847eed 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -27,6 +27,8 @@
int xen_set_wallclock(unsigned long time);
unsigned long long xen_sched_clock(void);
+bool xen_vcpu_stolen(int vcpu);
+
void xen_mark_init_mm_pinned(void);
void __init xen_fill_possible_map(void);