[PATCH 6.6 127/299] xen: evtchn: Allow shared registration of IRQ handers

Greg Kroah-Hartman
2024-02-27T13:53:53Z

From: Viresh Kumar <viresh.kumar@linaro.org>

[ Upstream commit 9e90e58c11b74c2bddac4b2702cf79d36b981278 ]

Currently the handling of events is supported either in the kernel or
userspace, but not both.

In order to support fast delivery of interrupts from the guest to the
backend, we need to handle the Queue notify part of Virtio protocol in
kernel and the rest in userspace.

Update the interrupt handler registration flag to IRQF_SHARED for event
channels, which would allow multiple entities to bind their interrupt
handler for the same event channel port.

Also increment the reference count of irq_info when multiple entities
try to bind event channel to irqchip, so the unbinding happens only
after all the users are gone.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/99b1edfd3147c6b5d22a5139dab5861e767dc34a.1697439990.git.viresh.kumar@linaro.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Stable-dep-of: fa765c4b4aed ("xen/events: close evtchn after mapping cleanup")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/xen/events/events_base.c | 3 ++-
drivers/xen/evtchn.c | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index c50419638ac0a..cd33a418344a8 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -1235,7 +1235,8 @@ static int bind_evtchn_to_irq_chip(evtchn_port_t evtchn, struct irq_chip *chip,
bind_evtchn_to_cpu(evtchn, 0, false);
} else {
struct irq_info *info = info_for_irq(irq);
- WARN_ON(info == NULL || info->type != IRQT_EVTCHN);
+ if (!WARN_ON(!info || info->type != IRQT_EVTCHN))
+ info->refcnt++;
}

out:
diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
index 9139a7364df53..59717628ca42b 100644
--- a/drivers/xen/evtchn.c
+++ b/drivers/xen/evtchn.c
@@ -397,7 +397,7 @@ static int evtchn_bind_to_user(struct per_user_data *u, evtchn_port_t port,
if (rc < 0)
goto err;

- rc = bind_evtchn_to_irqhandler_lateeoi(port, evtchn_interrupt, 0,
+ rc = bind_evtchn_to_irqhandler_lateeoi(port, evtchn_interrupt, IRQF_SHARED,
u->name, evtchn);
if (rc < 0)
goto err;
--
2.43.0