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

From: Baptiste Reynal
Date: Wed Mar 18 2015 - 09:39:16 EST

Hello Alex,

The module solution seems fine for me, I have no argument against it.
I used your patch on my tests, they are running ok.

Regards,
Baptiste

On Wed, Mar 18, 2015 at 12:04 AM, Alex Williamson
<alex.williamson@xxxxxxxxxx> wrote:
> 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@xxxxxxxxxxxxxxxxxxxxxx>
>> >
>> > 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@xxxxxxxxxxxxxxxxxxxxxx>
>> > Signed-off-by: Baptiste Reynal <b.reynal@xxxxxxxxxxxxxxxxxxxxxx>
>> > ---
>> > 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@xxxxxxxxxx>
> 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@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>"
> +#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 *),
>
>
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