Re: [Xen-devel] [RFC v3 3/6] xen/arm: Add save/restore support for ARM arch timer

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 05/12/2014 09:35 AM, Ian Campbell wrote:
> On Sun, 2014-05-11 at 09:58 +0100, Julien Grall wrote:
>> Hi Wei,
>>
>> Thank you for the patch.
>>
>> On 08/05/14 22:18, Wei Huang wrote:
>>> +    switch ( ctxt.type )
>>> +    {
>>> +    case ARM_TIMER_TYPE_PHYS:
>>> +        t = &v->arch.phys_timer;
>>> +        d->arch.phys_timer_base.offset = ctxt.vtb_offset;
>>> +        break;
>>> +    case ARM_TIMER_TYPE_VIRT:
>>> +        t = &v->arch.virt_timer;
>>> +        d->arch.virt_timer_base.offset = ctxt.vtb_offset;
>>
>> It seems you forgot to address some of my comments on the timer 
>> save/restore.
>>
>> Saving {virt,phys}_timer_base.offset per VCPU rather than per-domain 
>> seems a waste of space and confusing.
> 
> Is it 100% inconceivable that two vcpus might some day have different
> timers?

By timers, did you mean did different boot offset?

AFAIU, the timer counter (CNTP) is common to every {p,v{CPUs and
contains the number of ticks from the start time.

If some days we want to have two vcpus with different offfset, then we
can extend the format.

Regards,

-- 
Julien Grall

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