On Fri, Nov 8, 2013 at 12:11 PM, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> wrote: > On Fri, 2013-11-08 at 15:05 +1100, Benjamin Herrenschmidt wrote: >> On Fri, 2013-11-08 at 04:10 +0100, Alexander Graf wrote: >> > On 08.11.2013, at 03:44, Liu Ping Fan <kernelfans@xxxxxxxxx> wrote: >> > >> > > syscall is a very common behavior inside guest, and this patch >> > > optimizes the path for the emulation of BOOK3S_INTERRUPT_SYSCALL, >> > > so hypervisor can return to guest without heavy exit, i.e, no need >> > > to swap TLB, HTAB,.. etc >> > >> > The syscall exit you touch here only happens when you do an sc > 0 >> > with MSR_PR set inside the guest. The only case you realistically see >> > this is when you run PR KVM inside of an HV KVM guest. >> > >> > I don't think we should optimize for that case. Instead, we should >> > rather try to not bounce to the 1st hypervisor in the first place in >> > that scenario :). >> >> Well, so unfortunately openstack CI uses PR inside HV pretty >> heavily .... it *might* be worthwhile optimizing that path if the patch >> is simple enough... I'd make that Paul's call. > > Note that this is a statement of value for the idea ... not the > implementation ;-) From a quick look with Paulus, the patch is quite > broken. I'll let Paul comment in details. > Thank you very much, Regards, Pingfan -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
