> > From: Like Xu <like.xu@xxxxxxxxx> > > > > This patch adds support to KVM to save/restore the lbr stack on vCPU > > context switching. > > > > When the guest sets the ACTIVE bit of MSR_KVM_PV_LBR_CTRL, a perf event > > is created on the host for the related vCPU. This perf event ensures the > > LBR stack to be saved/restored when the vCPU thread is scheduled out/in. > > The perf event is removed and freed when the guest clears the ACTIVE > > bit. > > > > What about live migration? Does LBR stack need to be saved on the source side and > restored on the dest side with the passthrough mode? Yes it should. Either for call stack LBR, or when it is frozen/disabled. When it's not frozen/disabled and not in call stack LBR mode it likely doesn't hurt either, but it's not strictly needed because it will be replaced so quickly. -Andi
