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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.09.15 at 10:31, <kouya@xxxxxxxxxxxxxx> wrote:
> 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.

It would of course be helpful to understand 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.

Together with the above, and with or without code adjustment, I'd
then like to ask for a v2 with an improved description. And please
don't forget to Cc maintainers of the code as well as Wei (the 4.6
release manager).

Jan


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