Date: Thu, 17 Dec 2015 15:39:10 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org,
        Jason Wang <jasowang@redhat.com>, qemu-devel@nongnu.org,
        Alexander Duyck <alexander.duyck@gmail.com>
Subject: Re: [PATCH] virtio_ring: use smp_store_mb
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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.
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