Re: [Xen-devel] [Qemu-devel] [PATCH v2 6/9] xen/9pfs: receive requests from the frontend

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 15 Mar 2017, Greg Kurz wrote:
> On Mon, 13 Mar 2017 16:55:57 -0700
> Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
> 
> > Upon receiving an event channel notification from the frontend, schedule
> > the bottom half. From the bottom half, read one request from the ring,
> > create a pdu and call pdu_submit to handle it.
> > 
> > For now, only handle one request per ring at a time.
> > 
> > Signed-off-by: Stefano Stabellini <stefano@xxxxxxxxxxx>
> > CC: anthony.perard@xxxxxxxxxx
> > CC: jgross@xxxxxxxx
> > CC: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> > CC: Greg Kurz <groug@xxxxxxxx>
> > ---
> 
> Oops, one more remark I forgot in my the previous mail. See below.
> 
> >  hw/9pfs/xen-9p-backend.c | 47 
> > +++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 47 insertions(+)
> > 
> > diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
> > index 0e4a133..741dd31 100644
> > --- a/hw/9pfs/xen-9p-backend.c
> > +++ b/hw/9pfs/xen-9p-backend.c
> > @@ -94,12 +94,59 @@ static int xen_9pfs_init(struct XenDevice *xendev)
> >      return 0;
> >  }
> >  
> > +static int xen_9pfs_receive(struct Xen9pfsRing *ring)
> > +{
> > +    struct xen_9pfs_header h;
> > +    RING_IDX cons, prod, masked_prod, masked_cons;
> > +    V9fsPDU *pdu;
> > +
> > +    if (ring->inprogress) {
> > +        return 0;
> > +    }
> > +
> > +    cons = ring->intf->out_cons;
> > +    prod = ring->intf->out_prod;
> > +    xen_rmb();
> > +
> > +    if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) < sizeof(h)) {
> > +        return 0;
> > +    }
> > +    ring->inprogress = true;
> > +
> > +    masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
> > +    masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
> > +
> > +    xen_9pfs_read_packet(ring->ring.out, masked_prod, &masked_cons,
> > +                         XEN_9PFS_RING_SIZE, (uint8_t*) &h, sizeof(h));
> > +
> > +    pdu = pdu_alloc(&ring->priv->state);
> > +    pdu->size = h.size;
> 
> 9P uses little-endian, so this should be:
> 
>     pdu->size = le32_to_cpu(h.size);
> 
> > +    pdu->id = h.id;
> > +    pdu->tag = h.tag;
> 
> and:
> 
>     pdu->tag = le16_to_cpu(h.tag);
> 
> > +    ring->out_size = h.size;
> > +    ring->out_cons = cons + h.size;
> 
> Same here.

OK, thanks. Xen doesn't support big endian today, but they don't hurt.


> > +
> > +    qemu_co_queue_init(&pdu->complete);
> > +    pdu_submit(pdu);
> > +
> > +    return 0;
> > +}
> > +
> >  static void xen_9pfs_bh(void *opaque)
> >  {
> > +    struct Xen9pfsRing *ring = opaque;
> > +    xen_9pfs_receive(ring);
> >  }
> >  
> >  static void xen_9pfs_evtchn_event(void *opaque)
> >  {
> > +    struct Xen9pfsRing *ring = opaque;
> > +    evtchn_port_t port;
> > +
> > +    port = xenevtchn_pending(ring->evtchndev);
> > +    xenevtchn_unmask(ring->evtchndev, port);
> > +
> > +    qemu_bh_schedule(ring->bh);
> >  }
> >  
> >  static int xen_9pfs_free(struct XenDevice *xendev)
> 
> 

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