[PATCH] vfio: Split virqfd into a separate module for vfio bus drivers

From: Alex Williamson
Date: Wed Mar 18 2015 - 13:27:42 EST

An unintended consequence of commit 42ac9bd18d4f ("vfio: initialize
the virqfd workqueue in VFIO generic code") is that the vfio module
is renamed to vfio_core so that it can include both vfio and virqfd.
That's a user visible change that may break module loading scritps
and it imposes eventfd support as a dependency on the core vfio code,
which it's really not. virqfd is intended to be provided as a service
to vfio bus drivers, so instead of wrapping it into vfio.ko, we can
make it a stand-alone module toggled by vfio bus drivers. This has
the additional benefit of removing initialization and exit from the
core vfio code.

Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---

Posted in reply to "[PATCH v14 19/20] vfio: initialize the virqfd
workqueue in VFIO generic code", reposting as an official proposal.
I removed the Kconfig select from AMBA support. AMBA depends on
PLATFORM, which does the select and therefore seems sufficient.
Commit log and vfio_virqfd driver description also reworded.

drivers/vfio/Kconfig | 5 +++++
drivers/vfio/Makefile | 5 +++--
drivers/vfio/pci/Kconfig | 1 +
drivers/vfio/platform/Kconfig | 1 +
drivers/vfio/vfio.c | 8 --------
drivers/vfio/virqfd.c | 17 +++++++++++++++--
include/linux/vfio.h | 2 --
7 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
index d5322a4..7d092dd 100644
--- a/drivers/vfio/Kconfig
+++ b/drivers/vfio/Kconfig
@@ -13,6 +13,11 @@ config VFIO_SPAPR_EEH
depends on EEH && VFIO_IOMMU_SPAPR_TCE
default n

+config VFIO_VIRQFD
+ tristate
+ depends on VFIO && EVENTFD
+ default n
+
menuconfig VFIO
tristate "VFIO Non-Privileged userspace driver framework"
depends on IOMMU_API
diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
index d798b09..7b8a31f 100644
--- a/drivers/vfio/Makefile
+++ b/drivers/vfio/Makefile
@@ -1,6 +1,7 @@
-vfio_core-y := vfio.o virqfd.o
+vfio_virqfd-y := virqfd.o

-obj-$(CONFIG_VFIO) += vfio_core.o
+obj-$(CONFIG_VFIO) += vfio.o
+obj-$(CONFIG_VFIO_VIRQFD) += vfio_virqfd.o
obj-$(CONFIG_VFIO_IOMMU_TYPE1) += vfio_iommu_type1.o
obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o
obj-$(CONFIG_VFIO_SPAPR_EEH) += vfio_spapr_eeh.o
diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
index c6bb5da..579d83b 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -1,6 +1,7 @@
config VFIO_PCI
tristate "VFIO support for PCI devices"
depends on VFIO && PCI && EVENTFD
+ select VFIO_VIRQFD
help
Support for the PCI VFIO bus driver. This is required to make
use of PCI drivers using the VFIO framework.
diff --git a/drivers/vfio/platform/Kconfig b/drivers/vfio/platform/Kconfig
index c0a3bff..9a4403e 100644
--- a/drivers/vfio/platform/Kconfig
+++ b/drivers/vfio/platform/Kconfig
@@ -1,6 +1,7 @@
config VFIO_PLATFORM
tristate "VFIO support for platform devices"
depends on VFIO && EVENTFD && ARM
+ select VFIO_VIRQFD
help
Support for platform devices with VFIO. This is required to make
use of platform devices present on the system using the VFIO
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 86aac7e..0d33662 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1552,11 +1552,6 @@ static int __init vfio_init(void)
if (ret)
goto err_cdev_add;

- /* Start the virqfd cleanup handler used by some VFIO bus drivers */
- ret = vfio_virqfd_init();
- if (ret)
- goto err_virqfd;
-
pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");

/*
@@ -1569,8 +1564,6 @@ static int __init vfio_init(void)

return 0;

-err_virqfd:
- cdev_del(&vfio.group_cdev);
err_cdev_add:
unregister_chrdev_region(vfio.group_devt, MINORMASK);
err_alloc_chrdev:
@@ -1585,7 +1578,6 @@ static void __exit vfio_cleanup(void)
{
WARN_ON(!list_empty(&vfio.group_list));

- vfio_virqfd_exit();
idr_destroy(&vfio.group_idr);
cdev_del(&vfio.group_cdev);
unregister_chrdev_region(vfio.group_devt, MINORMASK);
diff --git a/drivers/vfio/virqfd.c b/drivers/vfio/virqfd.c
index 3d19aaf..27c89cd 100644
--- a/drivers/vfio/virqfd.c
+++ b/drivers/vfio/virqfd.c
@@ -13,12 +13,17 @@
#include <linux/vfio.h>
#include <linux/eventfd.h>
#include <linux/file.h>
+#include <linux/module.h>
#include <linux/slab.h>

+#define DRIVER_VERSION "0.1"
+#define DRIVER_AUTHOR "Alex Williamson <alex.williamson@xxxxxxxxxx>"
+#define DRIVER_DESC "IRQFD support for VFIO bus drivers"
+
static struct workqueue_struct *vfio_irqfd_cleanup_wq;
static DEFINE_SPINLOCK(virqfd_lock);

-int __init vfio_virqfd_init(void)
+static int __init vfio_virqfd_init(void)
{
vfio_irqfd_cleanup_wq =
create_singlethread_workqueue("vfio-irqfd-cleanup");
@@ -28,7 +33,7 @@ int __init vfio_virqfd_init(void)
return 0;
}

-void vfio_virqfd_exit(void)
+static void __exit vfio_virqfd_exit(void)
{
destroy_workqueue(vfio_irqfd_cleanup_wq);
}
@@ -211,3 +216,11 @@ void vfio_virqfd_disable(struct virqfd **pvirqfd)
flush_workqueue(vfio_irqfd_cleanup_wq);
}
EXPORT_SYMBOL_GPL(vfio_virqfd_disable);
+
+module_init(vfio_virqfd_init);
+module_exit(vfio_virqfd_exit);
+
+MODULE_VERSION(DRIVER_VERSION);
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 683b514..cbed15f 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -142,8 +142,6 @@ struct virqfd {
struct virqfd **pvirqfd;
};

-extern int vfio_virqfd_init(void);
-extern void vfio_virqfd_exit(void);
extern int vfio_virqfd_enable(void *opaque,
int (*handler)(void *, void *),
void (*thread)(void *, void *),

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