Rusty Russell wrote:
On Sunday 09 December 2007 09:02:48 Anthony Liguori wrote:
If QEMU ever got true SMP support, then virtio would not work as it
requires 16-bit atomic writes which AFAIK is not possible on a number of
non-x86 architectures.
Hmm? Where is this requirement coming from?
I think everyone should stop using the word "atomic" in virtio discussions;
it's confusing.
The virtio ring queue indices are 16-bit and are readable to one end
while writable on the other end. To ensure that this can be done in a
lock-less way, it's necessary to atomically update the index. Atomic is
the right word here because if the 16-bit write gets converted into two
8-bit writes, then very bad things could happen with SMP.
Regards,
Anthony Liguori
Rusty.