Il 01/05/2013 18:34, Chegu Vinod ha scritto: > On 5/1/2013 8:40 AM, Paolo Bonzini wrote: >>> I shall make the suggested changes. >>> Appreciate your review feedback on this part of the change. > Hi Paolo., > > Thanks for taking a look (BTW, I accidentally left out the "RFC" in the > patch subject line...my bad!). >> Hi Vinod, >> >> I think unfortunately it is not acceptable to make this patch work only >> for KVM. (It cannot work for Xen, but that's not a problem since Xen >> uses a different migration mechanism; but it should work for TCG). > > Ok. I hadn't yet looked at TCG aspects etc. Will follow up offline...
If we do it right with run_on_cpu, it should just work with TCG. >> Unfortunately, as you noted the run_on_cpu callbacks currently run >> under the big QEMU lock. We need to fix that first. We have time >> for that during 1.6. > > Ok. Was under the impression that anytime a vcpu thread enters to do > anything in qemu the BQL had to be held. So choose to go with > run_on_cpu() . Will follow up offline on alternatives run_on_cpu() is fine, but the problem is: 1) that run_on_cpu() is synchronous, so the migration thread is paused too; 2) doing the usleep directly in kvm_cpu_exec. > "Holding" the vcpus in the host context (i.e. kvm module) itself is > perhaps another way. Would need some handshakes (i.e. new ioctls ) with > the kernel. Would that be acceptable way to proceed? No, I think it's better to make the wait in userspace. KVM could help finding the CPUs to be stunned, since it is where the dirty bits are computed. Paolo
