On Mon, Aug 23, 2021 at 11:19:56PM +0200, Michael S. Tsirkin wrote: > On Mon, Aug 23, 2021 at 10:14:37AM +0200, Vincent Whitchurch wrote: > > vhost always uses SMP-conditional barriers, but these may not be > > sufficient when vhost is used to communicate between heterogeneous > > processors in an AMP configuration, especially since they're NOPs on > > !SMP builds. > > > > To solve this, use the virtio_*() barrier functions and ask them for > > non-weak barriers if requested by userspace. > > > > Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx> > > I am inclined to say let's (ab)use VIRTIO_F_ORDER_PLATFORM for this. > Jason what do you think? OK, thanks, I'll look into that. > Also is the use of DMA variants really the intended thing here? Could > you point me at some examples please? I'm using this on an ARM-based SoC. The main processor is a Cortex-A53 (arm64) and this processor runs the virtio drivers. The SoC also has another processor which is a Cortex-A5 (arm32) and this processor runs the virtio device end using vhost. There is no coherency between these two processors and to each other they look like any other DMA-capable hardware.
