Wednesday, January 9, 2019 5:50 PM, Michael S. Tsirkin: > alejandro.luc...@netronome.com; Daniel Marcovitch > <dani...@mellanox.com> > Subject: Re: [dpdk-dev] [PATCH v2] net/virtio: add platform memory > ordering feature support > > On Wed, Jan 09, 2019 at 05:34:38PM +0300, Ilya Maximets wrote: > > virtio_mb() is really heavy. I'd like to avoid it somehow, but I don't > > know how to do this yet. > > Linux driver doesn't avoid it either.
I understand v3 was merged but still would like to continue the discuss and make sure all is clear and agreed. Form patch [1] description it is very clear why we need the rte_smp_mb() barrier. However I am not sure why this barrier is interoperate into rte_mb in case of vDPA. In vDPA case, both read of the user ring and write of the avail index are for local cached memory. The only write which is to uncachable memory (device memory) is the notify itself. As I mentioned, there is a need to have a store fence before doing the notify, but from different reasons. So vDPA use case and need Is a bit different than what presented in [1]. [1] https://patches.dpdk.org/patch/49545/ > > -- > MST
