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Re: [libvirt] PATCH: Xen PCI device passthrough



On Tue, Mar 31, 2009 at 10:10:14AM +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> > +static const char *
> > +pciFindStubDriver(virConnectPtr conn)
> > +{
> > +    char drvpath[PATH_MAX];
> > +    int probed = 0;
> > +
> > +recheck:
> > +    pciDriverDir(drvpath, sizeof(drvpath), "pci-stub");
> > +    if (virFileExists(drvpath))
> > +        return "pci-stub";
> > +    pciDriverDir(drvpath, sizeof(drvpath), "pciback");
> > +    if (virFileExists(drvpath))
> > +        return "pciback";
> > +
> > +    if (!probed) {
> > +        const char *const stubprobe[] = { MODPROBE, "pci-stub", NULL };
> > +        const char *const backprobe[] = { MODPROBE, "pciback", NULL };on xen.
> 
> > +
> > +        probed = 1;
> > +        if (virRun(conn, stubprobe, NULL) < 0 &&
> > +            virRun(conn, backprobe, NULL) < 0) {
> >              char ebuf[1024];
> > -            VIR_WARN(_("modprobe %s failed: %s"), stub_module,
> > +            VIR_WARN(_("failed to load pci-stub or pciback drivers: %s"),
> >                       virStrerror(errno, ebuf, sizeof ebuf));
> > +            return 0;
> >          }
> > +
> > +        goto recheck;
> >      }
> 
> I'd tend to reverse that ordering.  It isn't a issue today, but once
> pv_ops/dom0 gets pciback support you might actually have both modules
> present for a given kernel.
> 
> pci-stub doesn't do anything special and will load just fine in any
> environment.  pciback is xen-specific (especially the part which handles
> pci passthrough to pv domains) and should not load when not running on xen.

Ahh, I was assuming that pciback would just go the way of the dodo
when dom0 pvops merged. I had forgotten it would still be needed for
pure PV pci passthrough without VT-d. So reversing it seems reasonable

Regards,
Daniel
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