Re: [Qemu-devel] [PATCH 3/3] xen: ignore direction in bufioreq handling

[Stefano Stabellini]

On Wed, 23 Nov 2016, Paul Durrant wrote:
> > -----Original Message-----
> > From: Jan Beulich [mailto:address@hidden
> > Sent: 23 November 2016 09:25
> > To: address@hidden
> > Cc: Anthony Perard <address@hidden>; Paul Durrant
> > <address@hidden>; Stefano Stabellini <address@hidden>; xen-
> > devel <address@hidden>
> > Subject: [PATCH 3/3] xen: ignore direction in bufioreq handling
> > 
> > There's no way to communicate back read data, so only writes can ever
> > be usefully specified. Ignore the field, paving the road for eventually
> > re-using the bit for something else in a few (many?) years time.
> > 
> > Signed-off-by: Jan Beulich <address@hidden>
> 
> Reviewed-by: Paul Durrant <address@hidden>

Acked-by: Stefano Stabellini <address@hidden>


> > 
> > --- a/xen-hvm.c
> > +++ b/xen-hvm.c
> > @@ -997,6 +997,7 @@ static int handle_buffered_iopage(XenIOS
> >      memset(&req, 0x00, sizeof(req));
> >      req.state = STATE_IOREQ_READY;
> >      req.count = 1;
> > +    req.dir = IOREQ_WRITE;
> > 
> >      for (;;) {
> >          uint32_t rdptr = buf_page->read_pointer, wrptr;
> > @@ -1014,7 +1015,6 @@ static int handle_buffered_iopage(XenIOS
> >          req.size = 1U << buf_req->size;
> >          req.addr = buf_req->addr;
> >          req.data = buf_req->data;
> > -        req.dir = buf_req->dir;
> >          req.type = buf_req->type;
> >          xen_rmb();
> >          qw = (req.size == 8);
> > @@ -1031,10 +1031,12 @@ static int handle_buffered_iopage(XenIOS
> >          handle_ioreq(state, &req);
> > 
> >          /* Only req.data may get updated by handle_ioreq(), albeit even 
> > that
> > -         * should not happen as such data would never make it to the guest.
> > +         * should not happen as such data would never make it to the guest 
> > (we
> > +         * can only usefully see writes here after all).
> >           */
> >          assert(req.state == STATE_IOREQ_READY);
> >          assert(req.count == 1);
> > +        assert(req.dir == IOREQ_WRITE);
> >          assert(!req.data_is_ptr);
> > 
> >          atomic_add(&buf_page->read_pointer, qw + 1);
> > 
> > 
>