Re: [PATCH v14 19/20] vfio: initialize the virqfd workqueue in VFIO generic code

Alex Williamson
2015-03-17T23:04:48Z

On Tue, 2015-03-17 at 16:29 -0600, Alex Williamson wrote:
> On Mon, 2015-03-02 at 17:59 +0100, Baptiste Reynal wrote:
> > From: Antonios Motakis <a.motakis@virtualopensystems.com>
> >
> > Now we have finally completely decoupled virqfd from VFIO_PCI. We can
> > initialize it from the VFIO generic code, in order to safely use it from
> > multiple independent VFIO bus drivers.
> >
> > Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
> > Signed-off-by: Baptiste Reynal <b.reynal@virtualopensystems.com>
> > ---
> > drivers/vfio/Makefile | 4 +++-
> > drivers/vfio/pci/Makefile | 3 +--
> > drivers/vfio/pci/vfio_pci.c | 8 --------
> > drivers/vfio/vfio.c | 8 ++++++++
> > 4 files changed, 12 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
> > index dadf0ca..d798b09 100644
> > --- a/drivers/vfio/Makefile
> > +++ b/drivers/vfio/Makefile
> > @@ -1,4 +1,6 @@
> > -obj-$(CONFIG_VFIO) += vfio.o
> > +vfio_core-y := vfio.o virqfd.o
> > +
> > +obj-$(CONFIG_VFIO) += vfio_core.o
> > obj-$(CONFIG_VFIO_IOMMU_TYPE1) += vfio_iommu_type1.o
> > obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o
> > obj-$(CONFIG_VFIO_SPAPR_EEH) += vfio_spapr_eeh.o
>
> This inadvertently (I assume) renames the main vfio module to vfio_core.
> That potentially breaks numerous userspace scripts that might try to
> load the "vfio" module. I don't think that's acceptable. A brute force
> way to fix this would be to rename vfio.c to vfio_core.c and change the
> Makefile to:
>
> vfio-y := vfio_core.o virqfd.o
> obj-$(CONFIG_VFIO) += vfio.o
>
> Is there any other trickery available to us that could include virqfd.o
> in vfio.o w/o source file renaming? Thanks,

Maybe a better option, we could let virqfd be it's own support module
for bus drivers that need it. Then we keep it out of vfio "core".
Something like this:

commit f4d91ec4b72ce11e9dba861d6bf2dba93b72f0ba
Author: Alex Williamson <alex.williamson@redhat.com>
Date: Tue Mar 17 08:33:38 2015 -0600

vfio: Split virqfd into a separate module for vfio bus drivers

An unintended consequence of splittng virqfd support to be shared
by bus drivers is renaming the core vfio module to vfio_core. This
is not very friendly to user scripts that may try to load the vfio
module. To resolve that and to make it clear that virqfd is a bus
driver service and not a dependency of vfio core, move this to a
separate module on which the bus drivers will depend.

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

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..4ec14af 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
@@ -11,6 +12,7 @@ config VFIO_PLATFORM
config VFIO_AMBA
tristate "VFIO support for AMBA devices"
depends on VFIO_PLATFORM && ARM_AMBA
+ select VFIO_VIRQFD
help
Support for ARM AMBA devices with VFIO. This is required to make
use of ARM AMBA 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..ede0ca1 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@redhat.com>"
+#define DRIVER_DESC "VFIO virqfd"
+
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 *),