Re: [PATCH v2] vp_vdpa: harden the logic of set status

[Longpeng (Mike, Cloud Infrastructure Service Product Dept.)]

在 2022/12/6 19:00, Stefano Garzarella 写道:
> On Tue, Dec 06, 2022 at 10:13:21AM +0800, Longpeng(Mike) wrote:
> > From: Longpeng <longpeng2@xxxxxxxxxx>
> >
> > 1. We should not set status to 0 when invoking vp_vdpa_set_status(),
> >   trigger a warning in that case.
> >
> > 2. The driver MUST wait for a read of device_status to return 0 before
> >   reinitializing the device. But we also don't want to keep us in an
> >   infinite loop forever, so wait for 5s if we try to reset the device.
> >
> > Signed-off-by: Longpeng <longpeng2@xxxxxxxxxx>
> > ---
> > Changes v1->v2:
> >  - use WARN_ON instead of BUG_ON. [Stefano]
> >  - use "warning + failed" instead of "infinite loop". [Jason, Stefano]
> >  - use usleep_range instead of msleep (checkpatch). [Longpeng]
> >
> > ---
> > drivers/vdpa/virtio_pci/vp_vdpa.c | 22 ++++++++++++++++++++++
> > 1 file changed, 22 insertions(+)
> >
> > diff --git a/drivers/vdpa/virtio_pci/vp_vdpa.c 
> > b/drivers/vdpa/virtio_pci/vp_vdpa.c
> > index 13701c2a1963..a2d3b13ac646 100644
> > --- a/drivers/vdpa/virtio_pci/vp_vdpa.c
> > +++ b/drivers/vdpa/virtio_pci/vp_vdpa.c
> > @@ -214,6 +214,9 @@ static void vp_vdpa_set_status(struct vdpa_device 
> > *vdpa, u8 status)
> >     struct virtio_pci_modern_device *mdev = vp_vdpa_to_mdev(vp_vdpa);
> >     u8 s = vp_vdpa_get_status(vdpa);
> >
> > +    /* We should never be setting status to 0. */
> > +    WARN_ON(status == 0);
> > +
> >     if (status & VIRTIO_CONFIG_S_DRIVER_OK &&
> >         !(s & VIRTIO_CONFIG_S_DRIVER_OK)) {
> >         vp_vdpa_request_irq(vp_vdpa);
> > @@ -222,14 +225,33 @@ static void vp_vdpa_set_status(struct 
> > vdpa_device *vdpa, u8 status)
> >     vp_modern_set_status(mdev, status);
> > }
> >
> > +#define VP_VDPA_RESET_TMOUT_MS 5000 /* 5s */
>
> What about moving this define on top of this file?
> Near the other macro.
>
> And I would use TIMEOUT entirely.
Okay.

> > +
> > static int vp_vdpa_reset(struct vdpa_device *vdpa, bool clear)
> > {
> >     struct vp_vdpa *vp_vdpa = vdpa_to_vp(vdpa);
> >     struct virtio_pci_modern_device *mdev = vp_vdpa_to_mdev(vp_vdpa);
> >     u8 s = vp_vdpa_get_status(vdpa);
> > +    unsigned long timeout;
> >
> >     vp_modern_set_status(mdev, 0);
> >
> > +    /*
> > +     * As the virtio v1.1 spec (4.1.4.3.2) says: After writing 0 to
>
> I think we can refer to the lates v1.2 (the section should be the same).
Okay, will do in next version, thanks.

> > +     * device_status, the driver MUST wait for a read of device_status
> > +     * to return 0 before reinitializing the device.
> > +     * To avoid keep us here forever, we only wait for 5 seconds.
> > +     */
> > +    timeout = jiffies + msecs_to_jiffies(VP_VDPA_RESET_TMOUT_MS);
> > +    while (vp_modern_get_status(mdev)) {
> > +        usleep_range(1000, 1500);
> > +        if (time_after(jiffies, timeout)) {
> > +            dev_err(&mdev->pci_dev->dev,
> > +                "vp_vdpa: fail to reset device\n");
> > +            return -ETIMEDOUT;
> > +        }
> > +    }
> > +
> >     if (s & VIRTIO_CONFIG_S_DRIVER_OK)
> >         vp_vdpa_free_irq(vp_vdpa);
> >
> > --
> > 2.23.0
>
> The rest LGTM!
>
> Thanks,
> Stefano
>
>
> .