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Re: merge bouyer-xenpvh to HEAD

Le mer. 22 avr. 2020 à 22:26, Manuel Bouyer <bouyer%antioche.eu.org@localhost> a écrit :
> Maybe the backend block and network drivers too; I think they are protected
> by KERNEL_LOCK but I'm not completely sure (especially xbdback).

xenneback processing is protected by KERNEL_LOCK, both the event
handler and the softint. So should be fine. If we get MULTIPROCESSOR
for Dom0 it's also relatively straightforward to adjust to not rely on

xbdback is actually not MPSAFE. It runs request processing in a kernel
thread with held spinlock. The thread is created with KTHREAD_MPSAFE
and thus doesn't take KERNEL_LOCK() implicitly. Amusingly enough the
only MP-unsafe part is xbdback_iodone(), which takes KERNEL_LOCK()
explicitely, but this doesn't prevent the xbdback thread from
modifying internal state on other cpu. A quickest fix would be just to
remove the KTHREAD_MPSAFE from the thread. I'll fix this up, I'm
familiar with the area having recendly done some changes there.


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