Re: [Qemu-devel] [PATCH] virtio_ring: use smp_store_mb

[Michael S. Tsirkin]

On Thu, Dec 17, 2015 at 03:39:10PM +0100, Peter Zijlstra wrote:
> On Thu, Dec 17, 2015 at 04:33:44PM +0200, Michael S. Tsirkin wrote:
> > On Thu, Dec 17, 2015 at 02:57:26PM +0100, Peter Zijlstra wrote:
> > > 
> > > You could of course go fix that instead of mutilating things into
> > > sort-of functional state.
> > 
> > Yes, we'd just need to touch all architectures, all for
> > the sake of UP which almost no one uses.
> > Basically, we need APIs that explicitly are
> > for talking to another kernel on a different CPU on
> > the same SMP system, and implemented identically
> > between CONFIG_SMP and !CONFIG_SMP on all architectures.
> > 
> > Do you think this is something of general usefulness,
> > outside virtio?
> 
> I'm not aware of any other case, but if there are more parts of virt
> that need this then I see no problem adding it.
> 
> That is, virt in general is the only use-case that I can think of,
> because this really is an artifact of interfacing with an SMP host while
> running an UP kernel.
> 
> But I'm really not familiar with virt, so I do not know if there's more
> sites outside of virtio that could use this.
> 
> Touching all archs is a tad tedious, but its fairly straight forward.

Thanks, will take a stub at this.