Re: [Qemu-devel] [PATCH] virtio: Make memory barriers be memory barriers

[Michael S. Tsirkin]

On Thu, Sep 01, 2011 at 04:09:49PM +1000, David Gibson wrote:
> The virtio code already has memory barrier wmb() macros in the code.
> However they are was defined as no-ops.  The comment claims that real
> barriers are not necessary because the code does not run concurrent.
> However, with kvm and io-thread enabled, this is not true and this qemu
> code can indeed run concurrently with the guest kernel.  This does not
> cause problems on x86 due to it's strongly ordered storage model, but it
> causes a race leading to virtio errors on POWER which has a relaxed storage
> ordering model.

Why not limit the change to ppc then?

-- 
MST