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Message-ID: <20211109081042-mutt-send-email-mst@kernel.org>
Date: Tue, 9 Nov 2021 08:10:58 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: Jason Wang <jasowang@...hat.com>,
virtualization <virtualization@...ts.linux-foundation.org>,
Parav Pandit <parav@...dia.com>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vdpa: add driver_override support
On Mon, Nov 08, 2021 at 06:05:29PM +0100, Stefano Garzarella wrote:
> On Fri, Nov 5, 2021 at 4:01 AM Jason Wang <jasowang@...hat.com> wrote:
> >
> > On Fri, Nov 5, 2021 at 12:17 AM Stefano Garzarella <sgarzare@...hat.com> wrote:
> > >
> > > `driver_override` allows to control which of the vDPA bus drivers
> > > binds to a vDPA device.
> > >
> > > If `driver_override` is not set, the previous behaviour is followed:
> > > devices use the first vDPA bus driver loaded (unless auto binding
> > > is disabled).
> > >
> > > Tested on Fedora 34 with driverctl(8):
> > > $ modprobe virtio-vdpa
> > > $ modprobe vhost-vdpa
> > > $ modprobe vdpa-sim-net
> > >
> > > $ vdpa dev add mgmtdev vdpasim_net name dev1
> > >
> > > # dev1 is attached to the first vDPA bus driver loaded
> > > $ driverctl -b vdpa list-devices
> > > dev1 virtio_vdpa
> > >
> > > $ driverctl -b vdpa set-override dev1 vhost_vdpa
> > >
> > > $ driverctl -b vdpa list-devices
> > > dev1 vhost_vdpa [*]
> > >
> > > Note: driverctl(8) integrates with udev so the binding is
> > > preserved.
> > >
> > > Suggested-by: Jason Wang <jasowang@...hat.com>
> > > Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
> > > ---
> > > include/linux/vdpa.h | 2 ++
> > > drivers/vdpa/vdpa.c | 74 ++++++++++++++++++++++++++++++++++++++++++++
> > > 2 files changed, 76 insertions(+)
> > >
> > > diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
> > > index c3011ccda430..ae34015b37b7 100644
> > > --- a/include/linux/vdpa.h
> > > +++ b/include/linux/vdpa.h
> > > @@ -64,6 +64,7 @@ struct vdpa_mgmt_dev;
> > > * struct vdpa_device - representation of a vDPA device
> > > * @dev: underlying device
> > > * @dma_dev: the actual device that is performing DMA
> > > + * @driver_override: driver name to force a match
> >
> > This seems useless?
> >
> > > * @config: the configuration ops for this device.
> > > * @cf_mutex: Protects get and set access to configuration layout.
> > > * @index: device index
> > > @@ -76,6 +77,7 @@ struct vdpa_mgmt_dev;
> > > struct vdpa_device {
> > > struct device dev;
> > > struct device *dma_dev;
> > > + const char *driver_override;
> > > const struct vdpa_config_ops *config;
> > > struct mutex cf_mutex; /* Protects get/set config */
> > > unsigned int index;
> > > diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> > > index 7332a74a4b00..659231bbfee8 100644
> > > --- a/drivers/vdpa/vdpa.c
> > > +++ b/drivers/vdpa/vdpa.c
> > > @@ -52,8 +52,81 @@ static void vdpa_dev_remove(struct device *d)
> > > drv->remove(vdev);
> > > }
> > >
> > > +static int vdpa_dev_match(struct device *dev, struct device_driver *drv)
> > > +{
> > > + struct vdpa_device *vdev = dev_to_vdpa(dev);
> > > +
> > > + /* Check override first, and if set, only use the named driver */
> > > + if (vdev->driver_override)
> > > + return strcmp(vdev->driver_override, drv->name) == 0;
> > > +
> > > + /* Currently devices must be supported by all vDPA bus drivers */
> > > + return 1;
> > > +}
> > > +
> > > +static ssize_t driver_override_store(struct device *dev,
> > > + struct device_attribute *attr,
> > > + const char *buf, size_t count)
> > > +{
> > > + struct vdpa_device *vdev = dev_to_vdpa(dev);
> > > + const char *driver_override, *old;
> > > + char *cp;
> > > +
> > > + /* We need to keep extra room for a newline */
> > > + if (count >= (PAGE_SIZE - 1))
> > > + return -EINVAL;
> > > +
> > > + driver_override = kstrndup(buf, count, GFP_KERNEL);
> > > + if (!driver_override)
> > > + return -ENOMEM;
> > > +
> > > + cp = strchr(driver_override, '\n');
> > > + if (cp)
> > > + *cp = '\0';
> > > +
> > > + device_lock(dev);
> > > + old = vdev->driver_override;
> > > + if (strlen(driver_override)) {
> > > + vdev->driver_override = driver_override;
> > > + } else {
> > > + kfree(driver_override);
> > > + vdev->driver_override = NULL;
> > > + }
> > > + device_unlock(dev);
> > > +
> > > + kfree(old);
> > > +
> > > + return count;
> > > +}
> > > +
> > > +static ssize_t driver_override_show(struct device *dev,
> > > + struct device_attribute *attr, char *buf)
> > > +{
> > > + struct vdpa_device *vdev = dev_to_vdpa(dev);
> > > + ssize_t len;
> > > +
> > > + device_lock(dev);
> > > + len = snprintf(buf, PAGE_SIZE, "%s\n", vdev->driver_override);
> > > + device_unlock(dev);
> > > +
> > > + return len;
> > > +}
> > > +static DEVICE_ATTR_RW(driver_override);
> > > +
> > > +static struct attribute *vdpa_dev_attrs[] = {
> > > + &dev_attr_driver_override.attr,
> > > + NULL,
> > > +};
> > > +
> > > +static const struct attribute_group vdpa_dev_group = {
> > > + .attrs = vdpa_dev_attrs,
> > > +};
> > > +__ATTRIBUTE_GROUPS(vdpa_dev);
> > > +
> > > static struct bus_type vdpa_bus = {
> > > .name = "vdpa",
> > > + .dev_groups = vdpa_dev_groups,
> >
> > This reminds me that we probably need to document the sysfs interface
> > in Documentation/ABI/testing/sysfs-bus-vdpa.
> >
> > But it's not the fault of this patch which look good.
>
> Michael, Jason, about Documentation/ABI/testing/sysfs-bus-vdpa, do you
> think is better to send a follow up patch/series, maybe including also
> others entries (e.g. bind, unbind) or a v2 including the documentation
> of `driver_ovveride`?
>
> Thanks,
> Stefano
I'd include it as a patch in series.
--
MST
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