On Thu, 2012-05-17 at 17:09 -0500, Anthony Liguori wrote: > ld/st should not ever be used by device emulation because they use a concept > of > "target endianness" that doesn't exist for devices.
Hrm, there's a bit of both, some of them even have explicit endianness arguments and some of them are definitely used by bits of hw/* virtio core uses them directly as well but then virtio also does explicit barriers (though I need to double check whether it does enough of them in all the right places). > So no, I don't think you need to put barriers there as they should only be > used > by VCPU emulation code. I'm ok to leave them alone for now, I'll give a quick look at the various callers. > > Note that with the above, cpu_physical_memory_map and unmap will > > imply a barrier when using bounce buffers, it would make sense to also > > provide the same barrier when not. > > > > That does actually make sense for the same reason explained above, > > ie, when those are used for a DMA transfer via async IO, that guarantees > > ordering of the "block" vs. surrounding accesses even if accesses within > > the actual map/unmap region are not ordered vs. each other. > > > > Any objection ? > > I think so. I'd like to see a better comment about barrier usage at the top > of > the file or something like that too. Ok. Cheers, Ben. > Regards, > > Anthony Liguori > > > > > Cheers, > > Ben. > > > > > >
