Re: [Qemu-devel] [PULL 0/19] xen-2015-09-08-tag

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Sep 10, 2015 at 12:26:21PM +0100, Stefano Stabellini wrote:
> On Thu, 10 Sep 2015, Michael S. Tsirkin wrote:
> > On Thu, Sep 10, 2015 at 11:29:18AM +0100, Stefano Stabellini wrote:
> > > CC Michael
> > > 
> > > On Thu, 10 Sep 2015, Stefano Stabellini wrote:
> > > > On Thu, 10 Sep 2015, Chen, Tiejun wrote:
> > > > > > xen-host-pci-device.c is only compiled if CONFIG_XEN_PCI_PASSTHROUGH
> > > > > > was set by configure. That won't be the case on OSX or Windows, where
> > > > > > the Xen headers don't exist.
> > > > > > 
> > > > > 
> > > > > Okay. This actually shouldn't be enabled on Windows so what about this?
> > > > 
> > > > I think it would be nicer to replace the pread than introducing ifdefs.
> > > 
> > > Something like:
> > > 
> > > ---
> > > Replace pread with read to avoid build breakages on Windows
> > > 
> > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > 
> > I'd prefer a wrapper that does the right thing.
> > No sense in doubling the # of system calls for everyone.
> 
> If this was done on an hot path I would agree with you, but it is just
> one call at initialization time (igd_pt_i440fx_initfn).

I missed this fact. OK then.

> 
> > > diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
> > > index 58a33fb..9a40429 100644
> > > --- a/hw/pci-host/piix.c
> > > +++ b/hw/pci-host/piix.c
> > > @@ -774,8 +774,11 @@ static int host_pci_config_read(int pos, int len, uint32_t val)
> > >          return -ENODEV;
> > >      }
> > >  
> > > +    if (lseek(config_fd, pos, SEEK_SET) != pos) {
> > > +        return -errno;
> > > +    }
> > >      do {
> > > -        rc = pread(config_fd, (uint8_t *)&val, len, pos);
> > > +        rc = read(config_fd, (uint8_t *)&val, len);
> > >      } while (rc < 0 && (errno == EINTR || errno == EAGAIN));
> > >      if (rc != len) {
> > >          return -errno;
> >