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SubjectRe: [Xen-devel] [PATCH 12/12] Unplug emulated disks and nics
On Thu, Jun 17, 2010 at 04:42:14PM +0100, Stefano Stabellini wrote:
> On Mon, 14 Jun 2010, Konrad Rzeszutek Wilk wrote:
> > > +#if (defined(CONFIG_XEN_NETDEV_FRONTEND) || \
> > > + defined(CONFIG_XEN_NETDEV_FRONTEND_MODULE)) && \
> > > + (defined(CONFIG_XEN_PLATFORM_PCI) || \
> > > + defined(CONFIG_XEN_PLATFORM_PCI_MODULE))
> > > + printk(KERN_INFO "Netfront and the Xen platform PCI driver have "
> > > + "been compiled for this kernel: unplug emulated NICs.\n");
> > > + xen_emul_unplug |= XEN_UNPLUG_ALL_NICS;
> > > +#endif
> > > +#if (defined(CONFIG_XEN_BLKDEV_FRONTEND) || \
> > > + defined(CONFIG_XEN_BLKDEV_FRONTEND_MODULE)) && \
> > > + (defined(CONFIG_XEN_PLATFORM_PCI) || \
> > > + defined(CONFIG_XEN_PLATFORM_PCI_MODULE))
> > > + printk(KERN_INFO "Blkfront and the Xen platform PCI driver have "
> > > + "been compiled for this kernel: unplug emulated disks.\n"
> > > + "You might have to change the root device\n"
> > > + "from /dev/hd[a-d] to /dev/xvd[a-d]\n"
> > > + "in your root= kernel command line option\n");
> > > + xen_emul_unplug |= XEN_UNPLUG_ALL_IDE_DISKS;
> > > +#endif
> >
> > Wow. Can you move those checks to the header file and make it deal with
> > the #ifdef and setting of xen_emul_unplug?
> >
>
> I tried, but it didn't improve the elegance of the code, mainly because I
> want to keep the printk in place, so the code would look very much like
> this, but instead of being in platform-pci-unplug.c would be in
> platform_pci.h.

If was thinking of something like this in the header file:


int xen_must_unplug_nics() {
#if (defined(CONFIG_XEN_NETDEV_FRONTEND) || \
defined(CONFIG_XEN_NETDEV_FRONTEND_MODULE)) && \
(defined(CONFIG_XEN_PLATFORM_PCI) || \
defined(CONFIG_XEN_PLATFORM_PCI_MODULE))
return 1;
#else
return 0;
}
and then your code would be:

if (xen_must_unplug_nics()) {
printk(".. blah blah ");
xen_emul_unplug |- XEN_unPLIG_ALL_NICS;
}
and similar for the IDE disks.

>
>
> > > + }
> > > + /* Now unplug the emulated devices */
> > > + if (xen_platform_pci_enabled && !(xen_emul_unplug & XEN_UNPLUG_IGNORE))
> > > + outw(xen_emul_unplug, XEN_IOPORT_UNPLUG);
> > > +}
> > > +
> > > +static int __init parse_xen_emul_unplug(char *arg)
> > > +{
> > > + char *p, *q;
> > > +
> > > + for (p = arg; p; p = q) {
> > > + q = strchr(arg, ',');
> > > + if (q)
> > > + *q++ = '\0';
> > > + if (!strcmp(p, "all"))
> > > + xen_emul_unplug |= XEN_UNPLUG_ALL;
> >
> > strncmp..
> >
>
> is it really needed considering that we know that both strings are NULL
> terminated and one of them is a constant?

Please do.


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