Messages in this thread | | | Date | Tue, 18 Sep 2018 17:57:50 +0800 | From | Wei Wang <> | Subject | Re: [PATCH v2 7/8] KVM: PMU: support to save/restore the guest lbr stack on vCPU switching |
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On 09/18/2018 10:56 AM, Andi Kleen wrote: >>> From: Like Xu <like.xu@intel.com> >>> >>> 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.
Yes, should be supported. We are working on v3 with the suggested lazy save approach, and will send it out shortly.
Best, Wei
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