From 9535989b80d89932f34f7f1596b91b400d7adbb2 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Mon, 5 Jul 2021 13:12:27 +0200 Subject: [PATCH] xen/events: reset active flag for lateeoi events later 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. This is commit 3de218ff39b9e3f0d453fe3154f12a174de44b25 upstream. Backport for Linux 5.10 and older. Cc: stable@xxxxxxxxxxxxxxx Reported-by: Julien Grall Fixes: b6622798bc50b62 ("xen/events: avoid handling the same event on two cpus at the same time") Tested-by: Julien Grall Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Link: https://lore.kernel.org/r/20210623130913.9405-1-jgross@xxxxxxxx --- drivers/xen/events/events_base.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c index 29bec0720514..af0f6ad32522 100644 --- a/drivers/xen/events/events_base.c +++ b/drivers/xen/events/events_base.c @@ -583,6 +583,9 @@ static void xen_irq_lateeoi_locked(struct irq_info *info, bool spurious) } 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); } @@ -1807,10 +1810,22 @@ static void lateeoi_ack_dynirq(struct irq_data *data) 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) -- 2.26.2