[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/2] xen: Fix determining when domain creation is complete
> -----Original Message----- > From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx] > Sent: 12 December 2016 18:30 > To: Xen-devel <xen-devel@xxxxxxxxxxxxx> > Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Jan Beulich > <JBeulich@xxxxxxxx>; Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Boris > Ostrovsky <boris.ostrovsky@xxxxxxxxxx> > Subject: [PATCH 2/2] xen: Fix determining when domain creation is complete > > d->creation_finished is used in several places alter behaviour depending on > whether the domain is being created, or is already running. > > However, there is a latent bug if a toolstack component makes a pair of > pause/unpause calls, where creation will be considered finished > prematurely. > > Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> > --- > CC: Jan Beulich <JBeulich@xxxxxxxx> > CC: Paul Durrant <paul.durrant@xxxxxxxxxx> I tested this on initial boot and restore. Tested-by: Paul Durrant <paul.durrant@xxxxxxxxxx> > CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> > > This is probably a backport candidate, as creation_finished was introduced in > 4.8 > --- > xen/common/domain.c | 21 ++++++++++++++------- > 1 file changed, 14 insertions(+), 7 deletions(-) > > diff --git a/xen/common/domain.c b/xen/common/domain.c > index 3abaca9..05130e2 100644 > --- a/xen/common/domain.c > +++ b/xen/common/domain.c > @@ -1004,13 +1004,6 @@ int domain_unpause_by_systemcontroller(struct > domain *d) > { > int old, new, prev = d->controller_pause_count; > > - /* > - * We record this information here for populate_physmap to figure out > - * that the domain has finished being created. In fact, we're only > - * allowed to set the MEMF_no_tlbflush flag during VM creation. > - */ > - d->creation_finished = true; > - > do > { > old = prev; > @@ -1022,6 +1015,20 @@ int domain_unpause_by_systemcontroller(struct > domain *d) > prev = cmpxchg(&d->controller_pause_count, old, new); > } while ( prev != old ); > > + /* > + * d->controller_pause_count is initialised to 1, and the toolstack is > + * responsible for making one unpause hypercall when it wishes the guest > + * to start running. > + * > + * All other toolstack operations should make a pair of pause/unpause > + * calls and rely on the reference counting here. > + * > + * Creation is considered finished when the controller reference count > + * first drops to 0. > + */ > + if ( new == 0 ) > + d->creation_finished = true; > + > domain_unpause(d); > > return 0; > -- > 2.1.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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