Re: [Xen-devel] [PATCH] x86/hvm: fix saved pmtimer value

[Kouya Shimura <kouya@xxxxxxxxxxxxxx>]

Jan Beulich <JBeulich@xxxxxxxx> writes:

>>>> On 09.09.15 at 09:31, <kouya@xxxxxxxxxxxxxx> wrote:
>> The ACPI PM timer is sometimes broken on live migration.
>> Since vcpu->arch.hvm_vcpu.guest_time is zero in most cases.
>
> I.e. in other than "delay for missed ticks mode". Would have been
> nice if you had spelled this out explicitly. 

Actually, I tried "delay for missed ticks mode" (timer_mode=0). 
Even in this case, the pmtimer was broken. I don't know why.

> With that the question then is - 
> should the field perhaps be used when non-zero, and the
> function only be called otherwise?

The adjustment of timer value in pmtimer_save() was introduced
before other timer_modes were implemented.

I'm not sure (skeptical) the small adjustment is really necessary 
in pmtimer_save.

Thanks,
Kouya

>
> Wei - regardless of the answer to the above (i.e. regardless of
> whether a v2 is going to be needed) I think we want this in 4.6.
>
> Jan

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