Re: [PATCH 10/11] xen/arch/x86: clarify domid == 0 checks

[Daniel De Graaf <dgdegra@tycho.nsa.gov>]

On 04/15/2013 04:51 AM, Jan Beulich wrote:
>>>> On 12.04.13 at 23:04, Daniel De Graaf <dgdegra@tycho.nsa.gov> wrote:
>> --- a/xen/arch/x86/time.c
>> +++ b/xen/arch/x86/time.c
>> @@ -1928,7 +1928,7 @@ void tsc_set_info(struct domain *d,
>>                     uint32_t tsc_mode, uint64_t elapsed_nsec,
>>                     uint32_t gtsc_khz, uint32_t incarnation)
>>   {
>> -    if ( is_idle_domain(d) || (d->domain_id == 0) )
>> +    if ( is_idle_domain(d) || is_hardware_domain(d) || is_control_domain(d)
>> )
>>       {
>>           d->arch.vtsc = 0;
>>           return;
>> @@ -2005,7 +2005,7 @@ static void dump_softtsc(unsigned char key)
>>                  "warp=%lu (count=%lu)\n", tsc_max_warp, tsc_check_count);
>>       for_each_domain ( d )
>>       {
>> -        if ( d->domain_id == 0 && d->arch.tsc_mode == TSC_MODE_DEFAULT )
>> +        if ( is_hardware_domain(d) && d->arch.tsc_mode == TSC_MODE_DEFAULT )
>>               continue;
>>           printk("dom%u%s: mode=%d",d->domain_id,
>>                   is_hvm_domain(d) ? "(hvm)" : "", d->arch.tsc_mode);
>
> I am of the opinion that the two checks should match, i.e. the
> second one should also become is_hardware || is_control. But
> I say this without really recalling why Dom0 is being special cased
> here in the first place.
>
> Jan
>

Since this is just an output function, my best guess is to avoid displaying
dom0 statistics that aren't relevant for a query that is intended for domUs,
so it doesn't really matter what is tested.

-- 
Daniel De Graaf
National Security Agency