On Wed, 23 Dec 2009 01:21:43 am Anthony Liguori wrote: > On 12/22/2009 05:26 AM, Michael S. Tsirkin wrote: > > On Tue, Dec 08, 2009 at 06:18:18PM +0200, Michael S. Tsirkin wrote: > > > >> The following fixes a class of long-standing bugs in qemu: > >> when kvm is enabled, guest might access device structures > >> in memory while they are updated by qemu on another CPU. > >> In this scenario, memory barriers are necessary to prevent > >> host CPU from reordering memory accesses, which might confuse > >> the guest. > >> > >> This patch only fixes virtio, but other emulated devices > >> might have a similar bug. They'll need to be discovered > >> and addressed case by case. > >> > >> This is still under test ... meanwhile: any early feedback/flames? > >> > >> > > Any comments on this one? > > The patch works fine in my testing, and even though > > it did not fix a crash that I hoped it will fix, > > it seems required for correctness... Right? > > > > It's definitely better than what we have. Rusty mentioned something to > me a bit ago about the barriers for virtio in the kernel needing some > work. I've been meaning to ask him about it in the context of this patch. > > Rusty, am I remembering correctly or have I been sipping too much > eggnog? :-)
It's possible, but I don't know of any missing cases. Certainly *lguest* i is missing barriers, since it's UP, but the core virtio should have them. Cheers, Rusty.
