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-rw-r--r--arch/x86/xen/smp.c172
-rw-r--r--drivers/xen/events.c27
-rw-r--r--include/asm-x86/xen/events.h1
-rw-r--r--include/xen/events.h7
4 files changed, 206 insertions, 1 deletions
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index a8ebafc09d47..e693812ac59a 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -15,6 +15,7 @@
* This does not handle HOTPLUG_CPU yet.
*/
#include <linux/sched.h>
+#include <linux/kernel_stat.h>
#include <linux/err.h>
#include <linux/smp.h>
@@ -35,6 +36,8 @@
#include "xen-ops.h"
#include "mmu.h"
+static void __cpuinit xen_init_lock_cpu(int cpu);
+
cpumask_t xen_cpu_initialized_map;
static DEFINE_PER_CPU(int, resched_irq);
@@ -179,6 +182,8 @@ static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
{
unsigned cpu;
+ xen_init_lock_cpu(0);
+
smp_store_cpu_info(0);
cpu_data(0).x86_max_cores = 1;
set_cpu_sibling_map(0);
@@ -301,6 +306,7 @@ static int __cpuinit xen_cpu_up(unsigned int cpu)
clear_tsk_thread_flag(idle, TIF_FORK);
#endif
xen_setup_timer(cpu);
+ xen_init_lock_cpu(cpu);
per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
@@ -413,6 +419,170 @@ static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id)
return IRQ_HANDLED;
}
+struct xen_spinlock {
+ unsigned char lock; /* 0 -> free; 1 -> locked */
+ unsigned short spinners; /* count of waiting cpus */
+};
+
+static int xen_spin_is_locked(struct raw_spinlock *lock)
+{
+ struct xen_spinlock *xl = (struct xen_spinlock *)lock;
+
+ return xl->lock != 0;
+}
+
+static int xen_spin_is_contended(struct raw_spinlock *lock)
+{
+ struct xen_spinlock *xl = (struct xen_spinlock *)lock;
+
+ /* Not strictly true; this is only the count of contended
+ lock-takers entering the slow path. */
+ return xl->spinners != 0;
+}
+
+static int xen_spin_trylock(struct raw_spinlock *lock)
+{
+ struct xen_spinlock *xl = (struct xen_spinlock *)lock;
+ u8 old = 1;
+
+ asm("xchgb %b0,%1"
+ : "+q" (old), "+m" (xl->lock) : : "memory");
+
+ return old == 0;
+}
+
+static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
+static DEFINE_PER_CPU(struct xen_spinlock *, lock_spinners);
+
+static inline void spinning_lock(struct xen_spinlock *xl)
+{
+ __get_cpu_var(lock_spinners) = xl;
+ wmb(); /* set lock of interest before count */
+ asm(LOCK_PREFIX " incw %0"
+ : "+m" (xl->spinners) : : "memory");
+}
+
+static inline void unspinning_lock(struct xen_spinlock *xl)
+{
+ asm(LOCK_PREFIX " decw %0"
+ : "+m" (xl->spinners) : : "memory");
+ wmb(); /* decrement count before clearing lock */
+ __get_cpu_var(lock_spinners) = NULL;
+}
+
+static noinline int xen_spin_lock_slow(struct raw_spinlock *lock)
+{
+ struct xen_spinlock *xl = (struct xen_spinlock *)lock;
+ int irq = __get_cpu_var(lock_kicker_irq);
+ int ret;
+
+ /* If kicker interrupts not initialized yet, just spin */
+ if (irq == -1)
+ return 0;
+
+ /* announce we're spinning */
+ spinning_lock(xl);
+
+ /* clear pending */
+ xen_clear_irq_pending(irq);
+
+ /* check again make sure it didn't become free while
+ we weren't looking */
+ ret = xen_spin_trylock(lock);
+ if (ret)
+ goto out;
+
+ /* block until irq becomes pending */
+ xen_poll_irq(irq);
+ kstat_this_cpu.irqs[irq]++;
+
+out:
+ unspinning_lock(xl);
+ return ret;
+}
+
+static void xen_spin_lock(struct raw_spinlock *lock)
+{
+ struct xen_spinlock *xl = (struct xen_spinlock *)lock;
+ int timeout;
+ u8 oldval;
+
+ do {
+ timeout = 1 << 10;
+
+ asm("1: xchgb %1,%0\n"
+ " testb %1,%1\n"
+ " jz 3f\n"
+ "2: rep;nop\n"
+ " cmpb $0,%0\n"
+ " je 1b\n"
+ " dec %2\n"
+ " jnz 2b\n"
+ "3:\n"
+ : "+m" (xl->lock), "=q" (oldval), "+r" (timeout)
+ : "1" (1)
+ : "memory");
+
+ } while (unlikely(oldval != 0 && !xen_spin_lock_slow(lock)));
+}
+
+static noinline void xen_spin_unlock_slow(struct xen_spinlock *xl)
+{
+ int cpu;
+
+ for_each_online_cpu(cpu) {
+ /* XXX should mix up next cpu selection */
+ if (per_cpu(lock_spinners, cpu) == xl) {
+ xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
+ break;
+ }
+ }
+}
+
+static void xen_spin_unlock(struct raw_spinlock *lock)
+{
+ struct xen_spinlock *xl = (struct xen_spinlock *)lock;
+
+ smp_wmb(); /* make sure no writes get moved after unlock */
+ xl->lock = 0; /* release lock */
+
+ /* make sure unlock happens before kick */
+ barrier();
+
+ if (unlikely(xl->spinners))
+ xen_spin_unlock_slow(xl);
+}
+
+static __cpuinit void xen_init_lock_cpu(int cpu)
+{
+ int irq;
+ const char *name;
+
+ name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
+ irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
+ cpu,
+ xen_reschedule_interrupt,
+ IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
+ name,
+ NULL);
+
+ if (irq >= 0) {
+ disable_irq(irq); /* make sure it's never delivered */
+ per_cpu(lock_kicker_irq, cpu) = irq;
+ }
+
+ printk("cpu %d spinlock event irq %d\n", cpu, irq);
+}
+
+static void __init xen_init_spinlocks(void)
+{
+ pv_lock_ops.spin_is_locked = xen_spin_is_locked;
+ pv_lock_ops.spin_is_contended = xen_spin_is_contended;
+ pv_lock_ops.spin_lock = xen_spin_lock;
+ pv_lock_ops.spin_trylock = xen_spin_trylock;
+ pv_lock_ops.spin_unlock = xen_spin_unlock;
+}
+
static const struct smp_ops xen_smp_ops __initdata = {
.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
.smp_prepare_cpus = xen_smp_prepare_cpus,
@@ -430,5 +600,5 @@ void __init xen_smp_init(void)
{
smp_ops = xen_smp_ops;
xen_fill_possible_map();
- paravirt_use_bytelocks();
+ xen_init_spinlocks();
}
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 332dd63750a0..0e0c28574af8 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -734,6 +734,33 @@ static void restore_cpu_ipis(unsigned int cpu)
}
}
+/* Clear an irq's pending state, in preparation for polling on it */
+void xen_clear_irq_pending(int irq)
+{
+ int evtchn = evtchn_from_irq(irq);
+
+ if (VALID_EVTCHN(evtchn))
+ clear_evtchn(evtchn);
+}
+
+/* Poll waiting for an irq to become pending. In the usual case, the
+ irq will be disabled so it won't deliver an interrupt. */
+void xen_poll_irq(int irq)
+{
+ evtchn_port_t evtchn = evtchn_from_irq(irq);
+
+ if (VALID_EVTCHN(evtchn)) {
+ struct sched_poll poll;
+
+ poll.nr_ports = 1;
+ poll.timeout = 0;
+ poll.ports = &evtchn;
+
+ if (HYPERVISOR_sched_op(SCHEDOP_poll, &poll) != 0)
+ BUG();
+ }
+}
+
void xen_irq_resume(void)
{
unsigned int cpu, irq, evtchn;
diff --git a/include/asm-x86/xen/events.h b/include/asm-x86/xen/events.h
index f8d57ea1f05f..8ded74720024 100644
--- a/include/asm-x86/xen/events.h
+++ b/include/asm-x86/xen/events.h
@@ -5,6 +5,7 @@ enum ipi_vector {
XEN_RESCHEDULE_VECTOR,
XEN_CALL_FUNCTION_VECTOR,
XEN_CALL_FUNCTION_SINGLE_VECTOR,
+ XEN_SPIN_UNLOCK_VECTOR,
XEN_NR_IPIS,
};
diff --git a/include/xen/events.h b/include/xen/events.h
index 67c4436554a9..4680ff3fbc91 100644
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -44,4 +44,11 @@ extern void notify_remote_via_irq(int irq);
extern void xen_irq_resume(void);
+/* Clear an irq's pending state, in preparation for polling on it */
+void xen_clear_irq_pending(int irq);
+
+/* Poll waiting for an irq to become pending. In the usual case, the
+ irq will be disabled so it won't deliver an interrupt. */
+void xen_poll_irq(int irq);
+
#endif /* _XEN_EVENTS_H */