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Date: Fri, 5 Nov 2021 16:26:44 +0800
From: Jason Wang <jasowang@...hat.com>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: virtualization <virtualization@...ts.linux-foundation.org>,
Parav Pandit <parav@...dia.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vdpa: add driver_override support
On Fri, Nov 5, 2021 at 4:05 PM Stefano Garzarella <sgarzare@...hat.com> wrote:
>
> On Fri, Nov 05, 2021 at 11:01:30AM +0800, Jason Wang 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?
>
> I'm a bit lost, do you mean we should remove the documentation of
> `driver_override`?
I misread the code which was misled by vdpa_mgmt_dev above:(
The code should be fine.
So:
Acked-by: Jason Wang <jasowang@...hat.com>
>
> >
> >> * @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.
> >
>
> Yeah, I'd like to add more documentation. We should also document the
> device life cycle and management API.
>
> It's on my to-do list, I'm prioritizing it!
>
> >But it's not the fault of this patch which look good.
>
> Thanks,
> Stefano
>
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