Re: [PATCH v10 04/17] vdpa: Fail the vdpa_reset() if fail to set device status to zero

[Jason Wang]

在 2021/8/3 下午5:31, Yongji Xie 写道:
> On Tue, Aug 3, 2021 at 3:58 PM Jason Wang <jasowang@xxxxxxxxxx> wrote:
> > 在 2021/7/29 下午3:34, Xie Yongji 写道:
> > > Re-read the device status to ensure it's set to zero during
> > > resetting. Otherwise, fail the vdpa_reset() after timeout.
> > >
> > > Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
> > > ---
> > >    include/linux/vdpa.h | 15 ++++++++++++++-
> > >    1 file changed, 14 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
> > > index 406d53a606ac..d1a80ef05089 100644
> > > --- a/include/linux/vdpa.h
> > > +++ b/include/linux/vdpa.h
> > > @@ -6,6 +6,7 @@
> > >    #include <linux/device.h>
> > >    #include <linux/interrupt.h>
> > >    #include <linux/vhost_iotlb.h>
> > > +#include <linux/delay.h>
> > >
> > >    /**
> > >     * struct vdpa_calllback - vDPA callback definition.
> > > @@ -340,12 +341,24 @@ static inline struct device *vdpa_get_dma_dev(struct vdpa_device *vdev)
> > >        return vdev->dma_dev;
> > >    }
> > >
> > > -static inline void vdpa_reset(struct vdpa_device *vdev)
> > > +#define VDPA_RESET_TIMEOUT_MS 1000
> > > +
> > > +static inline int vdpa_reset(struct vdpa_device *vdev)
> > >    {
> > >        const struct vdpa_config_ops *ops = vdev->config;
> > > +     int timeout = 0;
> > >
> > >        vdev->features_valid = false;
> > >        ops->set_status(vdev, 0);
> > > +     while (ops->get_status(vdev)) {
> > > +             timeout += 20;
> > > +             if (timeout > VDPA_RESET_TIMEOUT_MS)
> > > +                     return -EIO;
> > > +
> > > +             msleep(20);
> > > +     }
> >
> > I wonder if it's better to do this in the vDPA parent?
> >
> > Thanks
> Sorry, I didn't get you here. Do you mean vDPA parent driver (e.g.
> VDUSE)?


Yes, since the how it's expected to behave depends on the specific hardware.

Even for the spec, the behavior is transport specific:

PCI: requires reread until 0
MMIO: doesn't require but it might not work for the hardware so we 
decide to change
CCW: the succeed of the ccw command means the success of the reset

Thanks


> Actually I didn't find any other place where I can do
> set_status() and get_status().
>
> Thanks,
> Yongji