[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] cpu_down() but no cpu_up() in drivers/xen/cpu_hotplug.c ?
On Tue, 2010-05-11 at 10:34 +0100, Jan Beulich wrote: > Jeremy, > > how is pv-ops bringing up CPUs set to online in xenstore? Is this not > an automatic process (i.e. requires writing to respective online node > in sysfs), like in the traditional tree? The original commit which added CPU hotplug to pvops says: xen: implement CPU hotplugging Note the changes from 2.6.18-xen CPU hotplugging: A vcpu_down request from the remote admin via Xenbus both hotunplugs the CPU, and disables it by removing it from the cpu_present map, and removing its entry in /sys. A vcpu_up request from the remote admin only re-enables the CPU, and does not immediately bring the CPU up. A udev event is emitted, which can be caught by the user if he wishes to automatically re-up CPUs when available, or implement a more complex policy. Signed-off-by: Alex Nixon <alex.nixon@xxxxxxxxxx> Acked-by: Jeremy Fitzhardinge <jeremy@xxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> I'm not sure how the decision was reached to implement it this way, perhaps for consistency with CPU hotplug on other platforms/architectures? FWIW I use a udev rule to bring up CPUs as they are added, which is equivalent to the old behaviour: ACTION=="add", SUBSYSTEM=="cpu", RUN+="/bin/sh -c '[ ! -e /sys$devpath/online ] || echo 1 > /sys$devpath/online'" Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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