vfio: Introduce interface to flush virqfd inject workqueue

[ 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>

diff --git a/drivers/vfio/virqfd.c b/drivers/vfio/virqfd.c
index 414e98d82b02e561d5423910d0cb572b7c4ea7d3..b58ba030e7aef6250e090013673a1d07bc5e20ef 100644 (file)
--- a/drivers/vfio/virqfd.c
+++ b/drivers/vfio/virqfd.c
@@ -104,6 +104,13 @@ static void virqfd_inject(struct work_struct *work)
                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 *),
@@ -127,6 +134,7 @@ 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) {
@@ -217,6 +225,19 @@ void vfio_virqfd_disable(struct virqfd **pvirqfd)
 }
 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);
 

diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index b53a9557884adae600e07f0e4523aa70b030d651..b7275ed44e4cbacd50bbaaa4f1b84b1255285fb1 100644 (file)
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -243,6 +243,7 @@ struct virqfd {
        wait_queue_entry_t              wait;
        poll_table              pt;
        struct work_struct      shutdown;
+       struct work_struct      flush_inject;
        struct virqfd           **pvirqfd;
 };
 
@@ -251,5 +252,6 @@ extern int vfio_virqfd_enable(void *opaque,
                              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 */