* [Question about KVM on arm64] Consider putting VINVALL to deactivation @ 2020-01-14 14:20 Shaokun Zhang 2020-01-15 13:50 ` Marc Zyngier 0 siblings, 1 reply; 3+ messages in thread From: Shaokun Zhang @ 2020-01-14 14:20 UTC (permalink / raw) To: Marc Zyngier, Tangnianyao (ICT), kvmarm, linux-arm-kernel, fanhenglong, wanghaibin.wang Cc: Lizixian, wangwudi, jiayanlei Hi Marc, On activation, VMAPP command is followed by a VINVALL, which could be quite expensive for the start-up of virtual machine. If a vpeid is allowed successfully, it is not used in system. We may consider put VINVALL to deactivation to ensure all cache of certain vpeid is invalid, to simplify activation. We consider start-up may be more common and more time-consuming-sensitive than shutdown process. Do you think it's all right? Thanks, Shaokun _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Question about KVM on arm64] Consider putting VINVALL to deactivation 2020-01-14 14:20 [Question about KVM on arm64] Consider putting VINVALL to deactivation Shaokun Zhang @ 2020-01-15 13:50 ` Marc Zyngier 2020-01-16 6:21 ` Shaokun Zhang 0 siblings, 1 reply; 3+ messages in thread From: Marc Zyngier @ 2020-01-15 13:50 UTC (permalink / raw) To: Shaokun Zhang Cc: wangwudi, Lizixian, jiayanlei, fanhenglong, Tangnianyao (ICT), wanghaibin.wang, kvmarm, linux-arm-kernel Hi Shaokun, On 2020-01-14 14:20, Shaokun Zhang wrote: > Hi Marc, > > On activation, VMAPP command is followed by a VINVALL, which could be > quite expensive for the start-up of virtual machine. If a vpeid is > allowed > successfully, it is not used in system. How expensive? This is exactly similar to what happens on a physical machine where we perform an INVALL on MAPC. And yet you don't complain about that. Please provide numbers. > We may consider put VINVALL to deactivation to ensure all cache of > certain > vpeid is invalid, to simplify activation. We consider start-up may be > more > common and more time-consuming-sensitive than shutdown process. In my world, they cost the same thing, and happen just as often. Also, I want guarantees that on VMAPP, there is no stale information even if this is the first time we're using this VPEid (who knows what happens over kexec, for example). > Do you think it's all right? I don't, for the reasons stated above. You also provide no numbers showing how bad the overhead is, so I'm left guessing. Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Question about KVM on arm64] Consider putting VINVALL to deactivation 2020-01-15 13:50 ` Marc Zyngier @ 2020-01-16 6:21 ` Shaokun Zhang 0 siblings, 0 replies; 3+ messages in thread From: Shaokun Zhang @ 2020-01-16 6:21 UTC (permalink / raw) To: Marc Zyngier Cc: wangwudi, Lizixian, jiayanlei, fanhenglong, Tangnianyao (ICT), wanghaibin.wang, kvmarm, linux-arm-kernel Hi Marc, On 2020/1/15 21:50, Marc Zyngier wrote: > Hi Shaokun, > > On 2020-01-14 14:20, Shaokun Zhang wrote: >> Hi Marc, >> >> On activation, VMAPP command is followed by a VINVALL, which could be >> quite expensive for the start-up of virtual machine. If a vpeid is allowed >> successfully, it is not used in system. > > How expensive? This is exactly similar to what happens on a physical machine > where we perform an INVALL on MAPC. And yet you don't complain about that. > Agree, I didn't consider this before. > Please provide numbers. > >> We may consider put VINVALL to deactivation to ensure all cache of certain >> vpeid is invalid, to simplify activation. We consider start-up may be more >> common and more time-consuming-sensitive than shutdown process. > > In my world, they cost the same thing, and happen just as often. Also, I want > guarantees that on VMAPP, there is no stale information even if this is the > first time we're using this VPEid (who knows what happens over kexec, for > example). > >> Do you think it's all right? > > I don't, for the reasons stated above. You also provide no numbers showing > how bad the overhead is, so I'm left guessing. > Got it, you are right :-). Thanks for your explaination Shaokun > Thanks, > > M. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-01-16 6:22 UTC | newest] Thread overview: 3+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2020-01-14 14:20 [Question about KVM on arm64] Consider putting VINVALL to deactivation Shaokun Zhang 2020-01-15 13:50 ` Marc Zyngier 2020-01-16 6:21 ` Shaokun Zhang
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