vfio: move eventfd support code for VFIO_PCI to a separate file
The virqfd functionality that is used by VFIO_PCI to implement interrupt
masking and unmasking via an eventfd, is generic enough and can be reused
by another driver. Move it to a separate file in order to allow the code
to be shared.
Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
Signed-off-by: Baptiste Reynal <b.reynal@virtualopensystems.com>
Reviewed-by: Eric Auger <eric.auger@linaro.org>
Tested-by: Eric Auger <eric.auger@linaro.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
diff --git a/drivers/vfio/virqfd.c b/drivers/vfio/virqfd.c
new file mode 100644
index 0000000..5967899
--- /dev/null
+++ b/drivers/vfio/virqfd.c
@@ -0,0 +1,213 @@
+/*
+ * VFIO generic eventfd code for IRQFD support.
+ * Derived from drivers/vfio/pci/vfio_pci_intrs.c
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All rights reserved.
+ * Author: Alex Williamson <alex.williamson@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/vfio.h>
+#include <linux/eventfd.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+
+static struct workqueue_struct *vfio_irqfd_cleanup_wq;
+DEFINE_SPINLOCK(virqfd_lock);
+
+int __init vfio_virqfd_init(void)
+{
+ vfio_irqfd_cleanup_wq =
+ create_singlethread_workqueue("vfio-irqfd-cleanup");
+ if (!vfio_irqfd_cleanup_wq)
+ return -ENOMEM;
+
+ return 0;
+}
+
+void vfio_virqfd_exit(void)
+{
+ destroy_workqueue(vfio_irqfd_cleanup_wq);
+}
+
+static void virqfd_deactivate(struct virqfd *virqfd)
+{
+ queue_work(vfio_irqfd_cleanup_wq, &virqfd->shutdown);
+}
+
+static int virqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
+{
+ struct virqfd *virqfd = container_of(wait, struct virqfd, wait);
+ unsigned long flags = (unsigned long)key;
+
+ if (flags & POLLIN) {
+ /* An event has been signaled, call function */
+ if ((!virqfd->handler ||
+ virqfd->handler(virqfd->opaque, virqfd->data)) &&
+ virqfd->thread)
+ schedule_work(&virqfd->inject);
+ }
+
+ if (flags & POLLHUP) {
+ unsigned long flags;
+ spin_lock_irqsave(&virqfd_lock, flags);
+
+ /*
+ * The eventfd is closing, if the virqfd has not yet been
+ * queued for release, as determined by testing whether the
+ * virqfd pointer to it is still valid, queue it now. As
+ * with kvm irqfds, we know we won't race against the virqfd
+ * going away because we hold the lock to get here.
+ */
+ if (*(virqfd->pvirqfd) == virqfd) {
+ *(virqfd->pvirqfd) = NULL;
+ virqfd_deactivate(virqfd);
+ }
+
+ spin_unlock_irqrestore(&virqfd_lock, flags);
+ }
+
+ return 0;
+}
+
+static void virqfd_ptable_queue_proc(struct file *file,
+ wait_queue_head_t *wqh, poll_table *pt)
+{
+ struct virqfd *virqfd = container_of(pt, struct virqfd, pt);
+ add_wait_queue(wqh, &virqfd->wait);
+}
+
+static void virqfd_shutdown(struct work_struct *work)
+{
+ struct virqfd *virqfd = container_of(work, struct virqfd, shutdown);
+ u64 cnt;
+
+ eventfd_ctx_remove_wait_queue(virqfd->eventfd, &virqfd->wait, &cnt);
+ flush_work(&virqfd->inject);
+ eventfd_ctx_put(virqfd->eventfd);
+
+ kfree(virqfd);
+}
+
+static void virqfd_inject(struct work_struct *work)
+{
+ struct virqfd *virqfd = container_of(work, struct virqfd, inject);
+ if (virqfd->thread)
+ virqfd->thread(virqfd->opaque, virqfd->data);
+}
+
+int vfio_virqfd_enable(void *opaque,
+ int (*handler)(void *, void *),
+ void (*thread)(void *, void *),
+ void *data, struct virqfd **pvirqfd, int fd)
+{
+ struct fd irqfd;
+ struct eventfd_ctx *ctx;
+ struct virqfd *virqfd;
+ int ret = 0;
+ unsigned int events;
+
+ virqfd = kzalloc(sizeof(*virqfd), GFP_KERNEL);
+ if (!virqfd)
+ return -ENOMEM;
+
+ virqfd->pvirqfd = pvirqfd;
+ virqfd->opaque = opaque;
+ virqfd->handler = handler;
+ virqfd->thread = thread;
+ virqfd->data = data;
+
+ INIT_WORK(&virqfd->shutdown, virqfd_shutdown);
+ INIT_WORK(&virqfd->inject, virqfd_inject);
+
+ irqfd = fdget(fd);
+ if (!irqfd.file) {
+ ret = -EBADF;
+ goto err_fd;
+ }
+
+ ctx = eventfd_ctx_fileget(irqfd.file);
+ if (IS_ERR(ctx)) {
+ ret = PTR_ERR(ctx);
+ goto err_ctx;
+ }
+
+ virqfd->eventfd = ctx;
+
+ /*
+ * virqfds can be released by closing the eventfd or directly
+ * through ioctl. These are both done through a workqueue, so
+ * we update the pointer to the virqfd under lock to avoid
+ * pushing multiple jobs to release the same virqfd.
+ */
+ spin_lock_irq(&virqfd_lock);
+
+ if (*pvirqfd) {
+ spin_unlock_irq(&virqfd_lock);
+ ret = -EBUSY;
+ goto err_busy;
+ }
+ *pvirqfd = virqfd;
+
+ spin_unlock_irq(&virqfd_lock);
+
+ /*
+ * Install our own custom wake-up handling so we are notified via
+ * a callback whenever someone signals the underlying eventfd.
+ */
+ init_waitqueue_func_entry(&virqfd->wait, virqfd_wakeup);
+ init_poll_funcptr(&virqfd->pt, virqfd_ptable_queue_proc);
+
+ events = irqfd.file->f_op->poll(irqfd.file, &virqfd->pt);
+
+ /*
+ * Check if there was an event already pending on the eventfd
+ * before we registered and trigger it as if we didn't miss it.
+ */
+ if (events & POLLIN) {
+ if ((!handler || handler(opaque, data)) && thread)
+ schedule_work(&virqfd->inject);
+ }
+
+ /*
+ * Do not drop the file until the irqfd is fully initialized,
+ * otherwise we might race against the POLLHUP.
+ */
+ fdput(irqfd);
+
+ return 0;
+err_busy:
+ eventfd_ctx_put(ctx);
+err_ctx:
+ fdput(irqfd);
+err_fd:
+ kfree(virqfd);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(vfio_virqfd_enable);
+
+void vfio_virqfd_disable(struct virqfd **pvirqfd)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&virqfd_lock, flags);
+
+ if (*pvirqfd) {
+ virqfd_deactivate(*pvirqfd);
+ *pvirqfd = NULL;
+ }
+
+ spin_unlock_irqrestore(&virqfd_lock, flags);
+
+ /*
+ * Block until we know all outstanding shutdown jobs have completed.
+ * Even if we don't queue the job, flush the wq to be sure it's
+ * been released.
+ */
+ flush_workqueue(vfio_irqfd_cleanup_wq);
+}
+EXPORT_SYMBOL_GPL(vfio_virqfd_disable);