On Tue, May 03, 2011 at 04:39:01PM +0300, Gleb Natapov wrote: > > > > On Thu, Apr 28, 2011 at 12:52:03PM +0300, Gleb Natapov wrote: > > > > > KVM does not hold any references to rcu protected data when it > > > > > switches > > > > > CPU into a guest mode. In fact switching to a guest mode is very > > > > > similar > > > > > to exiting to userspase from rcu point of view. In addition CPU may > > > > > stay > > > > > in a guest mode for quite a long time (up to one time slice). Lets > > > > > treat > > > > > guest mode as quiescent state, just like we do with user-mode > > > > > execution. > > > > > > > > > > Signed-off-by: Gleb Natapov <g...@redhat.com> > > > > > --- > > > > > include/linux/kvm_host.h | 1 + > > > > > 1 files changed, 1 insertions(+), 0 deletions(-) > > > > > > > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > > > > index 0bc3d37..a347bce 100644 > > > > > --- a/include/linux/kvm_host.h > > > > > +++ b/include/linux/kvm_host.h > > > > > @@ -593,6 +593,7 @@ static inline void kvm_guest_enter(void) > > > > > { > > > > > account_system_vtime(current); > > > > > current->flags |= PF_VCPU; > > > > > + rcu_note_context_switch(smp_processor_id()); > > > > > } > > > > > > > > > > static inline void kvm_guest_exit(void) > > > > > -- > > > > > 1.7.2.3 > > > > > > > > Please have it in x86's vcpu_enter_guest, then its more explicit > > > > (uncertain about the context of kvm_guest_enter call in other arches). > > > > > > > I checked all of them and kvm_guest_enter() is always called with local > > > irq disabled. Paul confirmed that rcu_note_context_switch() can be > > > called in such context. > > > > OK then. Perhaps have an assert to verify interrupts are disabled? > Yes. Can add BUG_ON(preemptible()).
Also please add a comment to explain whats going on. The commit message above seems appropriate. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html