From 84ca7a8e45dafb49cd5ca90a343ba033e2885c17 Mon Sep 17 00:00:00 2001
From: David Vrabel <david.vrabel@citrix.com>
Date: Thu, 15 Aug 2013 13:21:06 +0100
Subject: xen/events: initialize local per-cpu mask for all possible events
The sizeof() argument in init_evtchn_cpu_bindings() is incorrect
resulting in only the first 64 (or 32 in 32-bit guests) ports having
their bindings being initialized to VCPU 0.
In most cases this does not cause a problem as request_irq() will set
the irq affinity which will set the correct local per-cpu mask.
However, if the request_irq() is called on a VCPU other than 0, there
is a window between the unmasking of the event and the affinity being
set were an event may be lost because it is not locally unmasked on
any VCPU. If request_irq() is called on VCPU 0 then local irqs are
disabled during the window and the race does not occur.
Fix this by initializing all NR_EVENT_CHANNEL bits in the local
per-cpu masks.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: stable@vger.kernel.org
---
drivers/xen/events.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
(limited to 'drivers/xen/events.c')
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index a58ac435a9a..a1ad5dae8ee 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -348,7 +348,7 @@ static void init_evtchn_cpu_bindings(void)
for_each_possible_cpu(i)
memset(per_cpu(cpu_evtchn_mask, i),
- (i == 0) ? ~0 : 0, sizeof(*per_cpu(cpu_evtchn_mask, i)));
+ (i == 0) ? ~0 : 0, NR_EVENT_CHANNELS/8);
}
static inline void clear_evtchn(int port)
--
cgit v1.2.3-70-g09d2
From 4704fe4f03a5ab27e3c36184af85d5000e0f8a48 Mon Sep 17 00:00:00 2001
From: David Vrabel <david.vrabel@citrix.com>
Date: Thu, 15 Aug 2013 13:21:07 +0100
Subject: xen/events: mask events when changing their VCPU binding
When a event is being bound to a VCPU there is a window between the
EVTCHNOP_bind_vpcu call and the adjustment of the local per-cpu masks
where an event may be lost. The hypervisor upcalls the new VCPU but
the kernel thinks that event is still bound to the old VCPU and
ignores it.
There is even a problem when the event is being bound to the same VCPU
as there is a small window beween the clear_bit() and set_bit() calls
in bind_evtchn_to_cpu(). When scanning for pending events, the kernel
may read the bit when it is momentarily clear and ignore the event.
Avoid this by masking the event during the whole bind operation.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
CC: stable@vger.kernel.org
---
drivers/xen/events.c | 11 +++++++++++
1 file changed, 11 insertions(+)
(limited to 'drivers/xen/events.c')
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index a1ad5dae8ee..5e8be462aed 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -1493,8 +1493,10 @@ void rebind_evtchn_irq(int evtchn, int irq)
/* Rebind an evtchn so that it gets delivered to a specific cpu */
static int rebind_irq_to_cpu(unsigned irq, unsigned tcpu)
{
+ struct shared_info *s = HYPERVISOR_shared_info;
struct evtchn_bind_vcpu bind_vcpu;
int evtchn = evtchn_from_irq(irq);
+ int masked;
if (!VALID_EVTCHN(evtchn))
return -1;
@@ -1510,6 +1512,12 @@ static int rebind_irq_to_cpu(unsigned irq, unsigned tcpu)
bind_vcpu.port = evtchn;
bind_vcpu.vcpu = tcpu;
+ /*
+ * Mask the event while changing the VCPU binding to prevent
+ * it being delivered on an unexpected VCPU.
+ */
+ masked = sync_test_and_set_bit(evtchn, BM(s->evtchn_mask));
+
/*
* If this fails, it usually just indicates that we're dealing with a
* virq or IPI channel, which don't actually need to be rebound. Ignore
@@ -1518,6 +1526,9 @@ static int rebind_irq_to_cpu(unsigned irq, unsigned tcpu)
if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_vcpu, &bind_vcpu) >= 0)
bind_evtchn_to_cpu(evtchn, tcpu);
+ if (!masked)
+ unmask_evtchn(evtchn);
+
return 0;
}
--
cgit v1.2.3-70-g09d2