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Re: [Xen-devel] [PATCH] xen/x86: Don't BUG on CPU0 offlining



On 06/28/2017 06:31 PM, Vitaly Kuznetsov wrote:
Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> writes:

On Mon, Jun 26, 2017 at 06:39:30PM +0200, Vitaly Kuznetsov wrote:
CONFIG_BOOTPARAM_HOTPLUG_CPU0 allows to offline CPU0 but Xen HVM guests
BUG() in xen_teardown_timer(). Remove the BUG_ON(), this is probably a
leftover from ancient times when CPU0 hotplug was impossible, it works
just fine for HVM.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

Perhaps:

BUG_ON(cpu == 0 && xen_pv_domain());


Linus says no BUG_ONs :-)

xen_pv_cpu_disable() has the following:

     if (cpu == 0)
             return -EBUSY;

as a protection so we won't get to xen_teardown_timer() but if you think
additional BUG_ON() protection is justified I'm definitely not against
adding it.

No, I don't think its needed. This should be handled at the appropriate
level, not down in the timer handling.

So:

Acked-by: Juergen Gross <jgross@xxxxxxxx>


Juergen


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