[PATCH 5.4 4/4] xen/events: reset active flag for lateeoi events later

Greg Kroah-Hartman
2021-07-09T13:20:42Z

From: Juergen Gross <jgross@suse.com>

commit 3de218ff39b9e3f0d453fe3154f12a174de44b25 upstream.

In order to avoid a race condition for user events when changing
cpu affinity reset the active flag only when EOI-ing the event.

This is working fine as all user events are lateeoi events. Note that
lateeoi_ack_mask_dynirq() is not modified as there is no explicit call
to xen_irq_lateeoi() expected later.

Cc: stable@vger.kernel.org
Reported-by: Julien Grall <julien@xen.org>
Fixes: b6622798bc50b62 ("xen/events: avoid handling the same event on two cpus at the same time")
Tested-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrvsky@oracle.com>
Link: https://lore.kernel.org/r/20210623130913.9405-1-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/xen/events/events_base.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)

--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -525,6 +525,9 @@ static void xen_irq_lateeoi_locked(struc
}

info->eoi_time = 0;
+
+ /* is_active hasn't been reset yet, do it now. */
+ smp_store_release(&info->is_active, 0);
do_unmask(info, EVT_MASK_REASON_EOI_PENDING);
}

@@ -1781,10 +1784,22 @@ static void lateeoi_ack_dynirq(struct ir
struct irq_info *info = info_for_irq(data->irq);
evtchn_port_t evtchn = info ? info->evtchn : 0;

- if (VALID_EVTCHN(evtchn)) {
- do_mask(info, EVT_MASK_REASON_EOI_PENDING);
- ack_dynirq(data);
- }
+ if (!VALID_EVTCHN(evtchn))
+ return;
+
+ do_mask(info, EVT_MASK_REASON_EOI_PENDING);
+
+ if (unlikely(irqd_is_setaffinity_pending(data)) &&
+ likely(!irqd_irq_disabled(data))) {
+ do_mask(info, EVT_MASK_REASON_TEMPORARY);
+
+ clear_evtchn(evtchn);
+
+ irq_move_masked_irq(data);
+
+ do_unmask(info, EVT_MASK_REASON_TEMPORARY);
+ } else
+ clear_evtchn(evtchn);
}

static void lateeoi_mask_ack_dynirq(struct irq_data *data)