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xen/events: avoid handling the same event on two cpus at the same time 

commit b6622798bc50b625a1e62f82c7190df40c1f5b21 upstream.

When changing the cpu affinity of an event it can happen today that
(with some unlucky timing) the same event will be handled on the old
and the new cpu at the same time.

Avoid that by adding an "event active" flag to the per-event data and
call the handler only if this flag isn't set.

Cc: stable@vger.kernel.org
Reported-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Link: https://lore.kernel.org/r/20210306161833.4552-4-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Juergen Gross 2021-03-15 09:22:38 +01:00 committed by Greg Kroah-Hartman
parent 92aefc62f4
commit b802b6ef28
2 changed files with 18 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
drivers/xen/events/events_base.c
View File

@ -694,6 +694,12 @@ static void xen_evtchn_close(unsigned int port)
BUG();
}
static void event_handler_exit(struct irq_info *info)
{
smp_store_release(&info->is_active, 0);
clear_evtchn(info->evtchn);
}
static void pirq_query_unmask(int irq)
{
struct physdev_irq_status_query irq_status;
@ -724,13 +730,13 @@ static void eoi_pirq(struct irq_data *data)
likely(!irqd_irq_disabled(data))) {
do_mask(info, EVT_MASK_REASON_TEMPORARY);
clear_evtchn(evtchn);
event_handler_exit(info);
irq_move_masked_irq(data);
do_unmask(info, EVT_MASK_REASON_TEMPORARY);
} else
clear_evtchn(evtchn);
event_handler_exit(info);
if (pirq_needs_eoi(data->irq)) {
rc = HYPERVISOR_physdev_op(PHYSDEVOP_eoi, &eoi);
@ -1566,6 +1572,8 @@ void handle_irq_for_port(evtchn_port_t port, struct evtchn_loop_ctrl *ctrl)
}
info = info_for_irq(irq);
if (xchg_acquire(&info->is_active, 1))
return;
if (ctrl->defer_eoi) {
info->eoi_cpu = smp_processor_id();
@ -1753,13 +1761,13 @@ static void ack_dynirq(struct irq_data *data)
likely(!irqd_irq_disabled(data))) {
do_mask(info, EVT_MASK_REASON_TEMPORARY);
clear_evtchn(evtchn);
event_handler_exit(info);
irq_move_masked_irq(data);
do_unmask(info, EVT_MASK_REASON_TEMPORARY);
} else
clear_evtchn(evtchn);
event_handler_exit(info);
}
static void mask_ack_dynirq(struct irq_data *data)
@ -1775,7 +1783,7 @@ static void lateeoi_ack_dynirq(struct irq_data *data)
if (VALID_EVTCHN(evtchn)) {
do_mask(info, EVT_MASK_REASON_EOI_PENDING);
clear_evtchn(evtchn);
event_handler_exit(info);
}
}
@ -1786,7 +1794,7 @@ static void lateeoi_mask_ack_dynirq(struct irq_data *data)
if (VALID_EVTCHN(evtchn)) {
do_mask(info, EVT_MASK_REASON_EXPLICIT);
clear_evtchn(evtchn);
event_handler_exit(info);
}
}
@ -1895,10 +1903,11 @@ 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);
struct irq_info *info = info_for_irq(irq);
evtchn_port_t evtchn = info ? info->evtchn : 0;
if (VALID_EVTCHN(evtchn))
clear_evtchn(evtchn);
event_handler_exit(info);
}
EXPORT_SYMBOL(xen_clear_irq_pending);
void xen_set_irq_pending(int irq)

1
drivers/xen/events/events_internal.h
View File

@ -38,6 +38,7 @@ struct irq_info {
#define EVT_MASK_REASON_EXPLICIT 0x01
#define EVT_MASK_REASON_TEMPORARY 0x02
#define EVT_MASK_REASON_EOI_PENDING 0x04
u8 is_active; /* Is event just being handled? */
unsigned irq;
unsigned int evtchn; /* event channel */
unsigned short cpu; /* cpu bound */