On Fri, Nov 5, 2021 at 4:01 AM Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
> On Fri, Nov 5, 2021 at 12:17 AM Stefano Garzarella <sgarzare@xxxxxxxxxx> 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@xxxxxxxxxx>
> > Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> > ---
> > 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
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