On Fri, May 15, 2015 at 04:43:33PM +0300, Nikita Kalyazin wrote: > Hi, > > > Maybe I missed a part of the discussion, but is there any special purpose for > using rte_mb (both read and write fence) here rather than rte_wmb (write > fence only)?
The fence is between write of used->idx and read of avail->flags, so rte_wmb won't do anything useful. > -- > > Best regards, > > Nikita Kalyazin, > n.kalyazin at samsung.com > > Software Engineer > CE OS Group > Samsung R&D Institute Russia > Tel: +7 (495) 797-25-00 #3816 > Tel: +7 (495) 797-25-03 > Office #1501, 12-1, Dvintsev str., > Moscow, 127018, Russia > > On Wed, May 13, 2015 at 12:46:30PM +0200, Thomas Monjalon wrote: > > 2015-04-29 19:11, Huawei Xie: > > > update of used->idx and read of avail->flags could be reordered. > > > memory fence should be used to ensure the order, otherwise guest could > > > see a stale used->idx value after it toggles the interrupt suppression > > > flag. > > > After guest sets the interrupt suppression flag, it will check if there > > > is more buffer to process through used->idx. If it sees a stale value, it > > > will exit the processing while host willn't send interrupt to guest. > > > > > > Signed-off-by: Huawei Xie <huawei.xie at intel.com> > > > > Applied with following title, thanks > > vhost: fix virtio freeze due to missed interrupt > >
