Re: [PATCH v3 2/5] vdpa: add vhost_vdpa_reset_status_fd

[Jason Wang]

On Thu, May 25, 2023 at 1:37 AM Eugenio Perez Martin
<eperezma@redhat.com> wrote:
>
> On Wed, May 17, 2023 at 7:49 AM Jason Wang <jasowang@redhat.com> wrote:
> >
> > On Wed, May 17, 2023 at 1:46 PM Eugenio Perez Martin
> > <eperezma@redhat.com> wrote:
> > >
> > > On Wed, May 17, 2023 at 5:14 AM Jason Wang <jasowang@redhat.com> wrote:
> > > >
> > > > On Tue, May 9, 2023 at 11:44 PM Eugenio Pérez <eperezma@redhat.com> 
> > > > wrote:
> > > > >
> > > > > This allows to reset a vhost-vdpa device from external subsystems like
> > > > > vhost-net, since it does not have any struct vhost_dev by the time we
> > > > > need to use it.
> > > > >
> > > > > It is used in subsequent patches to negotiate features
> > > > > and probe for CVQ ASID isolation.
> > > > >
> > > > > Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
> > > > > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > > > > ---
> > > > >  include/hw/virtio/vhost-vdpa.h |  1 +
> > > > >  hw/virtio/vhost-vdpa.c         | 58 
> > > > > +++++++++++++++++++++++-----------
> > > > >  2 files changed, 41 insertions(+), 18 deletions(-)
> > > > >
> > > > > diff --git a/include/hw/virtio/vhost-vdpa.h 
> > > > > b/include/hw/virtio/vhost-vdpa.h
> > > > > index c278a2a8de..28de7da91e 100644
> > > > > --- a/include/hw/virtio/vhost-vdpa.h
> > > > > +++ b/include/hw/virtio/vhost-vdpa.h
> > > > > @@ -54,6 +54,7 @@ typedef struct vhost_vdpa {
> > > > >      VhostVDPAHostNotifier notifier[VIRTIO_QUEUE_MAX];
> > > > >  } VhostVDPA;
> > > > >
> > > > > +void vhost_vdpa_reset_status_fd(int fd);
> > > > >  int vhost_vdpa_get_iova_range(int fd, struct vhost_vdpa_iova_range 
> > > > > *iova_range);
> > > > >
> > > > >  int vhost_vdpa_dma_map(struct vhost_vdpa *v, uint32_t asid, hwaddr 
> > > > > iova,
> > > > > diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> > > > > index bbabea18f3..7a2053b8d9 100644
> > > > > --- a/hw/virtio/vhost-vdpa.c
> > > > > +++ b/hw/virtio/vhost-vdpa.c
> > > > > @@ -335,38 +335,45 @@ static const MemoryListener 
> > > > > vhost_vdpa_memory_listener = {
> > > > >      .region_del = vhost_vdpa_listener_region_del,
> > > > >  };
> > > > >
> > > > > -static int vhost_vdpa_call(struct vhost_dev *dev, unsigned long int 
> > > > > request,
> > > > > -                             void *arg)
> > > > > +static int vhost_vdpa_dev_fd(const struct vhost_dev *dev)
> > > > >  {
> > > > >      struct vhost_vdpa *v = dev->opaque;
> > > > > -    int fd = v->device_fd;
> > > > > -    int ret;
> > > > >
> > > > >      assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
> > > > > +    return v->device_fd;
> > > > > +}
> > > >
> > > > Nit: unless the vhost_dev structure is opaque to the upper layer, I
> > > > don't see any advantage for having a dedicated indirect helper to get
> > > > device_fd.
> > > >
> > >
> > > The purpose was to not duplicate the assert, but sure it's not mandatory.
> >
> > Ok, but I think for new codes, we'd better avoid assert as much as possible.
> >
>
> I'll remove it, thanks!
>
> > >
> > > > > +
> > > > > +static int vhost_vdpa_call_fd(int fd, unsigned long int request, 
> > > > > void *arg)
> > > > > +{
> > > > > +    int ret = ioctl(fd, request, arg);
> > > > >
> > > > > -    ret = ioctl(fd, request, arg);
> > > > >      return ret < 0 ? -errno : ret;
> > > > >  }
> > > > >
> > > > > -static int vhost_vdpa_add_status(struct vhost_dev *dev, uint8_t 
> > > > > status)
> > > > > +static int vhost_vdpa_call(struct vhost_dev *dev, unsigned long int 
> > > > > request,
> > > > > +                           void *arg)
> > > > > +{
> > > > > +    return vhost_vdpa_call_fd(vhost_vdpa_dev_fd(dev), request, arg);
> > > > > +}
> > > > > +
> > > > > +static int vhost_vdpa_add_status_fd(int fd, uint8_t status)
> > > > >  {
> > > > >      uint8_t s;
> > > > >      int ret;
> > > > >
> > > > > -    trace_vhost_vdpa_add_status(dev, status);
> > > > > -    ret = vhost_vdpa_call(dev, VHOST_VDPA_GET_STATUS, &s);
> > > > > +    ret = vhost_vdpa_call_fd(fd, VHOST_VDPA_GET_STATUS, &s);
> > > > >      if (ret < 0) {
> > > > >          return ret;
> > > > >      }
> > > > >
> > > > >      s |= status;
> > > > >
> > > > > -    ret = vhost_vdpa_call(dev, VHOST_VDPA_SET_STATUS, &s);
> > > > > +    ret = vhost_vdpa_call_fd(fd, VHOST_VDPA_SET_STATUS, &s);
> > > > >      if (ret < 0) {
> > > > >          return ret;
> > > > >      }
> > > > >
> > > > > -    ret = vhost_vdpa_call(dev, VHOST_VDPA_GET_STATUS, &s);
> > > > > +    ret = vhost_vdpa_call_fd(fd, VHOST_VDPA_GET_STATUS, &s);
> > > > >      if (ret < 0) {
> > > > >          return ret;
> > > > >      }
> > > > > @@ -378,6 +385,12 @@ static int vhost_vdpa_add_status(struct 
> > > > > vhost_dev *dev, uint8_t status)
> > > > >      return 0;
> > > > >  }
> > > > >
> > > > > +static int vhost_vdpa_add_status(struct vhost_dev *dev, uint8_t 
> > > > > status)
> > > > > +{
> > > > > +    trace_vhost_vdpa_add_status(dev, status);
> > > > > +    return vhost_vdpa_add_status_fd(vhost_vdpa_dev_fd(dev), status);
> > > > > +}
> > > > > +
> > > > >  int vhost_vdpa_get_iova_range(int fd, struct vhost_vdpa_iova_range 
> > > > > *iova_range)
> > > > >  {
> > > > >      int ret = ioctl(fd, VHOST_VDPA_GET_IOVA_RANGE, iova_range);
> > > > > @@ -709,16 +722,20 @@ static int vhost_vdpa_get_device_id(struct 
> > > > > vhost_dev *dev,
> > > > >      return ret;
> > > > >  }
> > > > >
> > > > > +static int vhost_vdpa_reset_device_fd(int fd)
> > > > > +{
> > > > > +    uint8_t status = 0;
> > > > > +
> > > > > +    return vhost_vdpa_call_fd(fd, VHOST_VDPA_SET_STATUS, &status);
> > > > > +}
> > > > > +
> > > > >  static int vhost_vdpa_reset_device(struct vhost_dev *dev)
> > > > >  {
> > > > >      struct vhost_vdpa *v = dev->opaque;
> > > > > -    int ret;
> > > > > -    uint8_t status = 0;
> > > > >
> > > > > -    ret = vhost_vdpa_call(dev, VHOST_VDPA_SET_STATUS, &status);
> > > > > -    trace_vhost_vdpa_reset_device(dev);
> > > > >      v->suspended = false;
> > > > > -    return ret;
> > > > > +    trace_vhost_vdpa_reset_device(dev);
> > > > > +    return vhost_vdpa_reset_device_fd(vhost_vdpa_dev_fd(dev));
> > > > >  }
> > > > >
> > > > >  static int vhost_vdpa_get_vq_index(struct vhost_dev *dev, int idx)
> > > > > @@ -1170,6 +1187,13 @@ static int vhost_vdpa_dev_start(struct 
> > > > > vhost_dev *dev, bool started)
> > > > >      return 0;
> > > > >  }
> > > > >
> > > > > +void vhost_vdpa_reset_status_fd(int fd)
> > > > > +{
> > > > > +    vhost_vdpa_reset_device_fd(fd);
> > > > > +    vhost_vdpa_add_status_fd(fd, VIRTIO_CONFIG_S_ACKNOWLEDGE |
> > > > > +                                 VIRTIO_CONFIG_S_DRIVER);
> > > >
> > > > I would like to rename this function since it does more than just reset.
> > > >
> > >
> > > vhost_vdpa_set_ready?
> >
> > But it doesn't set DRIVER_OK so it might be somehow misleading.
> >
>
> I'm still thinking about this. I don't like the original name either
> (vhost_vdpa_reset_status), but that one was already in the code before
> this patch. To rename it makes this patch scope bigger.
>
> The main idea of this function is to stop duplicating code between
> net/vhost-vdpa and hw/virtio/vdpa. One possibility is to not export
> vhost_vdpa_reset_status_fd but export vhost_vdpa_reset_device_fd and
> vhost_vdpa_add_status_fd individually. Does that seem better?

Probably not, the reason is that at uAPI level, we don't differ reset
from other status actually:

#define VHOST_VDPA_SET_STATUS           _IOW(VHOST_VIRTIO, 0x72, __u8)

>
> The other end is not to offer anything and call raw ioctl as previous
> code of net/vhost-vdpa. There is a middle ground, like only exporting
> one of them for sure.

This might be better.

Thanks

>
> What do you think?
>
> Thanks!
>
> > Thanks
> >
> > >
> > > Thanks!
> > >
> > > > Thanks
> > > >
> > > > > +}
> > > > > +
> > > > >  static void vhost_vdpa_reset_status(struct vhost_dev *dev)
> > > > >  {
> > > > >      struct vhost_vdpa *v = dev->opaque;
> > > > > @@ -1178,9 +1202,7 @@ static void vhost_vdpa_reset_status(struct 
> > > > > vhost_dev *dev)
> > > > >          return;
> > > > >      }
> > > > >
> > > > > -    vhost_vdpa_reset_device(dev);
> > > > > -    vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE |
> > > > > -                               VIRTIO_CONFIG_S_DRIVER);
> > > > > +    vhost_vdpa_reset_status_fd(vhost_vdpa_dev_fd(dev));
> > > > >      memory_listener_unregister(&v->listener);
> > > > >  }
> > > > >
> > > > > --
> > > > > 2.31.1
> > > > >
> > > >
> > >
> >
>