[PATCH 5.4 141/215] vfio: Introduce interface to flush virqfd inject workqueue

Greg Kroah-Hartman
2024-04-11T10:20:59Z

From: Alex Williamson <alex.williamson@redhat.com>

[ Upstream commit b620ecbd17a03cacd06f014a5d3f3a11285ce053 ]

In order to synchronize changes that can affect the thread callback,
introduce an interface to force a flush of the inject workqueue. The
irqfd pointer is only valid under spinlock, but the workqueue cannot
be flushed under spinlock. Therefore the flush work for the irqfd is
queued under spinlock. The vfio_irqfd_cleanup_wq workqueue is re-used
for queuing this work such that flushing the workqueue is also ordered
relative to shutdown.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20240308230557.805580-4-alex.williamson@redhat.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/vfio/virqfd.c | 21 +++++++++++++++++++++
include/linux/vfio.h | 2 ++
2 files changed, 23 insertions(+)

--- a/drivers/vfio/virqfd.c
+++ b/drivers/vfio/virqfd.c
@@ -101,6 +101,13 @@ static void virqfd_inject(struct work_st
virqfd->thread(virqfd->opaque, virqfd->data);
}

+static void virqfd_flush_inject(struct work_struct *work)
+{
+ struct virqfd *virqfd = container_of(work, struct virqfd, flush_inject);
+
+ flush_work(&virqfd->inject);
+}
+
int vfio_virqfd_enable(void *opaque,
int (*handler)(void *, void *),
void (*thread)(void *, void *),
@@ -124,6 +131,7 @@ int vfio_virqfd_enable(void *opaque,

INIT_WORK(&virqfd->shutdown, virqfd_shutdown);
INIT_WORK(&virqfd->inject, virqfd_inject);
+ INIT_WORK(&virqfd->flush_inject, virqfd_flush_inject);

irqfd = fdget(fd);
if (!irqfd.file) {
@@ -214,6 +222,19 @@ void vfio_virqfd_disable(struct virqfd *
}
EXPORT_SYMBOL_GPL(vfio_virqfd_disable);

+void vfio_virqfd_flush_thread(struct virqfd **pvirqfd)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&virqfd_lock, flags);
+ if (*pvirqfd && (*pvirqfd)->thread)
+ queue_work(vfio_irqfd_cleanup_wq, &(*pvirqfd)->flush_inject);
+ spin_unlock_irqrestore(&virqfd_lock, flags);
+
+ flush_workqueue(vfio_irqfd_cleanup_wq);
+}
+EXPORT_SYMBOL_GPL(vfio_virqfd_flush_thread);
+
module_init(vfio_virqfd_init);
module_exit(vfio_virqfd_exit);

--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -186,6 +186,7 @@ struct virqfd {
wait_queue_entry_t wait;
poll_table pt;
struct work_struct shutdown;
+ struct work_struct flush_inject;
struct virqfd **pvirqfd;
};

@@ -194,5 +195,6 @@ extern int vfio_virqfd_enable(void *opaq
void (*thread)(void *, void *),
void *data, struct virqfd **pvirqfd, int fd);
extern void vfio_virqfd_disable(struct virqfd **pvirqfd);
+void vfio_virqfd_flush_thread(struct virqfd **pvirqfd);

#endif /* VFIO_H */