The Xen PV spinlock backend attempts to setup an IPI to IRQ binding
which is only to be used via xen_poll_irq rather received directly.
Unfortunately restore_cpu_ipis unconditionally unmasks each IPI
leading to:
[ 21.970432] ------------[ cut here ]------------
[ 21.970432] kernel BUG at
/local/scratch/ianc/devel/kernels/linux-2.6/arch/x86/xen/spinlock.c:343!
[ 21.970432] invalid opcode: 0000 [#1] SMP
[ 21.970432] last sysfs file: /sys/devices/virtual/net/lo/operstate
[ 21.970432] Modules linked in:
[ 21.970432]
[ 21.970432] Pid: 0, comm: swapper Not tainted
(2.6.32.24-x86_32p-xen-01034-g787c727 #34)
[ 21.970432] EIP: 0061:[<c102e209>] EFLAGS: 00010046 CPU: 3
[ 21.970432] EIP is at dummy_handler+0x3/0x7
[ 21.970432] EAX: 0000021c EBX: dfc16880 ECX: 0000001a EDX: 00000000
[ 21.970432] ESI: dfc02c00 EDI: 00000001 EBP: dfc47e10 ESP: dfc47e10
[ 21.970432] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0069
[ 21.970432] Process swapper (pid: 0, ti=dfc46000 task=dfc39440
task.ti=dfc46000)
[ 21.970432] Stack:
[ 21.970432] dfc47e30 c10a39f0 0000021c 00000000 00000000 dfc16880 0000021c
00000001
[ 21.970432] <0> dfc47e40 c10a4f08 0000021c 00000000 dfc47e78 c12240a7
c1839284 c1839284
[ 21.970432] <0> 00000200 00000000 00000000 f5720000 c1f3d028 c1f3d02c
00000180 dfc47e90
[ 21.970432] Call Trace:
[ 21.970432] [<c10a39f0>] ? handle_IRQ_event+0x5f/0x122
[ 21.970432] [<c10a4f08>] ? handle_percpu_irq+0x2f/0x55
[ 21.970432] [<c12240a7>] ? __xen_evtchn_do_upcall+0xdb/0x15f
[ 21.970432] [<c122481e>] ? xen_evtchn_do_upcall+0x20/0x30
[ 21.970432] [<c1030d47>] ? xen_do_upcall+0x7/0xc
[ 21.970432] [<c102007b>] ? apic_reg_read+0xd3/0x22d
[ 21.970432] [<c1002227>] ? hypercall_page+0x227/0x1005
[ 21.970432] [<c102d30b>] ? xen_force_evtchn_callback+0xf/0x14
[ 21.970432] [<c102da7c>] ? check_events+0x8/0xc
[ 21.970432] [<c102da3b>] ? xen_irq_enable_direct_end+0x0/0x1
[ 21.970432] [<c105e485>] ? finish_task_switch+0x62/0xba
[ 21.970432] [<c14e3f84>] ? schedule+0x808/0x89d
[ 21.970432] [<c1084dc5>] ? hrtimer_start_expires+0x1a/0x22
[ 21.970432] [<c1085154>] ? tick_nohz_restart_sched_tick+0x15a/0x162
[ 21.970432] [<c102f43a>] ? cpu_idle+0x6d/0x6f
[ 21.970432] [<c14db29e>] ? cpu_bringup_and_idle+0xd/0xf
[ 21.970432] Code: 5d 0f 95 c0 0f b6 c0 c3 55 66 83 78 02 00 89 e5 5d 0f 95
c0 0f b6 c0 c3 55 b2 01 86 10 31 c0 84 d2 89 e5 0f 94 c0 5d c3 55 89 e5 <0f> 0b
eb fe 55 80 3d 4c ce 84 c1 00 89 e5 57 56 89 c6 53 74 15
[ 21.970432] EIP: [<c102e209>] dummy_handler+0x3/0x7 SS:ESP 0069:dfc47e10
[ 21.970432] ---[ end trace c0b71f7e12cf3011 ]---
Add a new bind function which explicitly binds a polled-only IPI and
track this state in the event channel core so that we can do the right
thing on restore.
Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
arch/x86/xen/spinlock.c | 16 +++-------------
drivers/xen/events.c | 45 ++++++++++++++++++++++++++++++++++++++++-----
include/xen/events.h | 4 ++++
3 files changed, 47 insertions(+), 18 deletions(-)
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 36a5141..09655ca 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -338,29 +338,19 @@ static void xen_spin_unlock(struct raw_spinlock *lock)
xen_spin_unlock_slow(xl);
}
-static irqreturn_t dummy_handler(int irq, void *dev_id)
-{
- BUG();
- return IRQ_HANDLED;
-}
-
void __cpuinit 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,
+ irq = bind_polled_ipi_to_irq(XEN_SPIN_UNLOCK_VECTOR,
cpu,
- dummy_handler,
IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
- name,
- NULL);
+ name);
- if (irq >= 0) {
- disable_irq(irq); /* make sure it's never delivered */
+ if (irq >= 0)
per_cpu(lock_kicker_irq, cpu) = irq;
- }
printk("cpu %d spinlock event irq %d\n", cpu, irq);
}
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 7b29ae1..f8b53b5 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -94,7 +94,10 @@ struct irq_info
union {
unsigned short virq;
- enum ipi_vector ipi;
+ struct {
+ enum ipi_vector vector;
+ unsigned char polled;
+ } ipi;
struct {
unsigned short gsi;
unsigned char vector;
@@ -148,7 +151,7 @@ static struct irq_info mk_evtchn_info(unsigned short evtchn)
static struct irq_info mk_ipi_info(unsigned short evtchn, enum ipi_vector ipi)
{
return (struct irq_info) { .type = IRQT_IPI, .evtchn = evtchn,
- .cpu = 0, .u.ipi = ipi };
+ .cpu = 0, .u.ipi.vector = ipi, .u.ipi.polled = 0 };
}
static struct irq_info mk_virq_info(unsigned short evtchn, unsigned short virq)
@@ -191,7 +194,7 @@ static enum ipi_vector ipi_from_irq(unsigned irq)
BUG_ON(info == NULL);
BUG_ON(info->type != IRQT_IPI);
- return info->u.ipi;
+ return info->u.ipi.vector;
}
static unsigned virq_from_irq(unsigned irq)
@@ -971,6 +974,33 @@ int bind_ipi_to_irqhandler(enum ipi_vector ipi,
return irq;
}
+
+static irqreturn_t polled_ipi_handler(int irq, void *dev_id)
+{
+ BUG();
+ return IRQ_HANDLED;
+}
+
+int bind_polled_ipi_to_irq(enum ipi_vector ipi,
+ unsigned int cpu,
+ unsigned long irqflags,
+ const char *devname)
+{
+ int irq, retval;
+
+ irq = bind_ipi_to_irqhandler(ipi, cpu, polled_ipi_handler,
+ irqflags, devname, NULL);
+ if (irq < 0)
+ return irq;
+
+ info_for_irq(irq)->u.ipi.polled = 1;
+
+ disable_irq(irq); /* make sure it's never delivered */
+
+ return irq;
+
+}
+
void unbind_from_irqhandler(unsigned int irq, void *dev_id)
{
free_irq(irq, dev_id);
@@ -1290,6 +1320,7 @@ static void restore_cpu_virqs(unsigned int cpu)
static void restore_cpu_ipis(unsigned int cpu)
{
struct evtchn_bind_ipi bind_ipi;
+ int polled;
int ipi, irq, evtchn;
for (ipi = 0; ipi < XEN_NR_IPIS; ipi++) {
@@ -1306,12 +1337,16 @@ static void restore_cpu_ipis(unsigned int cpu)
evtchn = bind_ipi.port;
/* Record the new mapping. */
+ polled = info_for_irq(irq)->u.ipi.polled;
evtchn_to_irq[evtchn] = irq;
irq_info[irq] = mk_ipi_info(evtchn, ipi);
bind_evtchn_to_cpu(evtchn, cpu);
- /* Ready for use. */
- unmask_evtchn(evtchn);
+ /* Ready for use. Polled IPIs remain masked */
+ if (polled)
+ info_for_irq(irq)->u.ipi.polled = 1;
+ else
+ unmask_evtchn(evtchn);
}
}
diff --git a/include/xen/events.h b/include/xen/events.h
index 7e17e2a..b2f09ad 100644
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -24,6 +24,10 @@ int bind_ipi_to_irqhandler(enum ipi_vector ipi,
unsigned long irqflags,
const char *devname,
void *dev_id);
+int bind_polled_ipi_to_irq(enum ipi_vector ipi,
+ unsigned int cpu,
+ unsigned long irqflags,
+ const char *devname);
int bind_interdomain_evtchn_to_irqhandler(unsigned int remote_domain,
unsigned int remote_port,
irq_handler_t handler,
--
1.5.6.5
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