Re: [Qemu-devel] [PATCH 4/4] 9pfs: add a size parameter to init_iov_from_pdu

[Stefano Stabellini]

On Thu, 24 Nov 2016, Greg Kurz wrote:

> On Mon, 21 Nov 2016 13:39:32 -0800
> Stefano Stabellini <address@hidden> wrote:
> 
> > Not all 9pfs transports share memory between request and response. For
> > those who don't, it is necessary to know how much memory is required in
> > the response.
> > 
> > Signed-off-by: Stefano Stabellini <address@hidden>
> > ---
> 
> IIUC the transport used in Xen requires you pass the size when sending a
> P9_RREAD message back to the guest, i.e. only in the case when is_write is
> false, correct ?

That's right


> If so, for better clarity, what about having two distinct init_in_iov_from_pdu
> and init_out_iov_from_pdu ops, with an explicit comment in the virtio-9p
> implementation of init_in_iov_from_pdu so that someone isn't tempted to drop
> the apparently unused size argument ? Would this be ok for you on the Xen
> side ?

Sure, that's fine by me. I'll do that.


> Cheers.
> 
> --
> Greg
> 
> >  hw/9pfs/9p.c               | 2 +-
> >  hw/9pfs/9p.h               | 2 +-
> >  hw/9pfs/virtio-9p-device.c | 2 +-
> >  3 files changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> > index b6ec042..b82212b 100644
> > --- a/hw/9pfs/9p.c
> > +++ b/hw/9pfs/9p.c
> > @@ -1652,7 +1652,7 @@ static void v9fs_init_qiov_from_pdu(QEMUIOVector 
> > *qiov, V9fsPDU *pdu,
> >      struct iovec *iov;
> >      unsigned int niov;
> >  
> > -    pdu->s->transport->init_iov_from_pdu(pdu, &iov, &niov, is_write);
> > +    pdu->s->transport->init_iov_from_pdu(pdu, &iov, &niov, is_write, skip 
> > + size);
> >  
> >      qemu_iovec_init_external(&elem, iov, niov);
> >      qemu_iovec_init(qiov, niov);
> > diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
> > index ab398d0..c830188 100644
> > --- a/hw/9pfs/9p.h
> > +++ b/hw/9pfs/9p.h
> > @@ -348,7 +348,7 @@ struct V9fsTransport {
> >      ssize_t     (*pdu_vmarshal)(V9fsPDU *pdu, size_t offset, const char 
> > *fmt, va_list ap);
> >      ssize_t     (*pdu_vunmarshal)(V9fsPDU *pdu, size_t offset, const char 
> > *fmt, va_list ap);
> >      void        (*init_iov_from_pdu)(V9fsPDU *pdu, struct iovec **piov,
> > -                              unsigned int *pniov, bool is_write);
> > +                              unsigned int *pniov, bool is_write, size_t 
> > size);
> >      void        (*push_and_notify)(V9fsPDU *pdu);
> >  };
> >  
> > diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c
> > index e1a37a4..e2b27e8 100644
> > --- a/hw/9pfs/virtio-9p-device.c
> > +++ b/hw/9pfs/virtio-9p-device.c
> > @@ -172,7 +172,7 @@ static ssize_t virtio_pdu_vunmarshal(V9fsPDU *pdu, 
> > size_t offset,
> >  }
> >  
> >  static void virtio_init_iov_from_pdu(V9fsPDU *pdu, struct iovec **piov,
> > -                              unsigned int *pniov, bool is_write)
> > +                              unsigned int *pniov, bool is_write, size_t 
> > size)
> >  {
> >      V9fsState *s = pdu->s;
> >      V9fsVirtioState *v = container_of(s, V9fsVirtioState, state);
>