# Re: \[PATCH\] virtio\_ring: switch to dma\_XX barriers for rpmsg

- From: Michael S. Tsirkin \<mst@redhat.com\>
- Date: 2018-05-30 14:10:56 
- List: virtualization
- Page: https://ratatoskr.run/virtualization/2018/05/15812296
- Thread: https://ratatoskr.run/virtualization/2018/05/15812296/t.md

```text
On Thu, Apr 19, 2018 at 07:48:24PM +0200, Paolo Bonzini wrote:
> On 19/04/2018 19:46, Michael S. Tsirkin wrote:
> >> This should be okay, but I wonder if there should be a virtio_wmb(...)
> >> or an "if (weak_barriers) wmb()" before the "writel" in vm_notify
> >> (drivers/virtio/virtio_mmio.c).
> >>
> >> Thanks,
> >>
> >> Paolo
> > That one uses weak barriers AFAIK.
> > 
> > IIUC you mean rproc_virtio_notify.
> > 
> > I suspect it works because specific kick callbacks have a barrier internally.
> 
> Yes, that one.  At least keystone_rproc_kick doesn't seem to have a barrier.
> 
> Paolo

Any feedback from rproc maintainers?

-- 
MST
```