* [Question about KVM on arm64] Consider putting VINVALL to deactivation
@ 2020-01-14 14:20 ` Shaokun Zhang
0 siblings, 0 replies; 6+ 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
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Question about KVM on arm64] Consider putting VINVALL to deactivation
@ 2020-01-14 14:20 ` Shaokun Zhang
0 siblings, 0 replies; 6+ 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] 6+ messages in thread
* Re: [Question about KVM on arm64] Consider putting VINVALL to deactivation
2020-01-14 14:20 ` Shaokun Zhang
@ 2020-01-15 13:50 ` Marc Zyngier
-1 siblings, 0 replies; 6+ messages in thread
From: Marc Zyngier @ 2020-01-15 13:50 UTC (permalink / raw)
To: Shaokun Zhang
Cc: wangwudi, Lizixian, jiayanlei, fanhenglong, 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...
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [Question about KVM on arm64] Consider putting VINVALL to deactivation
@ 2020-01-15 13:50 ` Marc Zyngier
0 siblings, 0 replies; 6+ 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] 6+ 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
-1 siblings, 0 replies; 6+ messages in thread
From: Shaokun Zhang @ 2020-01-16 6:21 UTC (permalink / raw)
To: Marc Zyngier
Cc: wangwudi, Lizixian, jiayanlei, fanhenglong, 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.
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Question about KVM on arm64] Consider putting VINVALL to deactivation
@ 2020-01-16 6:21 ` Shaokun Zhang
0 siblings, 0 replies; 6+ 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] 6+ messages in thread
end of thread, other threads:[~2020-01-16 6:22 UTC | newest]
Thread overview: 6+ 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
2020-01-14 14:20 ` Shaokun Zhang
2020-01-15 13:50 ` Marc Zyngier
2020-01-15 13:50 ` Marc Zyngier
2020-01-16 6:21 ` Shaokun Zhang
2020-01-16 6:21 ` Shaokun Zhang
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.