Re: merge bouyer-xenpvh to HEAD

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Wed, Apr 22, 2020 at 11:08:27PM +0200, Jaromír Dole?ek wrote:
> 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
> KERNEL_LOCK.
> 
> 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.

Good, thanks !

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--