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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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