On Tue, 2014-06-03 at 00:30 +0300, Michael S. Tsirkin wrote: > All memory accesses are done under some VQ mutex. > So lock/unlock all VQs is a faster equivalent of synchronize_rcu() > for memory access changes. > Some guests cause a lot of these changes, so it's helpful > to make them faster. > > Reported-by: "Gonglei (Arei)" <arei.gonglei@xxxxxxxxxx> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > --- > drivers/vhost/vhost.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 78987e4..1c05e60 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -593,6 +593,7 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) > { > struct vhost_memory mem, *newmem, *oldmem; > unsigned long size = offsetof(struct vhost_memory, regions); > + int i; > > if (copy_from_user(&mem, m, size)) > return -EFAULT; > @@ -619,7 +620,14 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) > oldmem = rcu_dereference_protected(d->memory, > lockdep_is_held(&d->mutex)); > rcu_assign_pointer(d->memory, newmem); > - synchronize_rcu(); > + > + /* All memory accesses are done under some VQ mutex. > + * So below is a faster equivalent of synchronize_rcu() > + */ > + for (i = 0; i < d->nvqs; ++i) { > + mutex_lock(&d->vqs[i]->mutex); > + mutex_unlock(&d->vqs[i]->mutex); > + } > kfree(oldmem); > return 0; > } This looks dubious What about using kfree_rcu() instead ? translate_desc() still uses rcu_read_lock(), its not clear if the mutex is really held. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization