Re: [Xen-devel] [PATCH v6 1/4] xen/libxc: Allow changing max number of hypervisor cpuid leaves

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.03.14 at 16:13, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:
> On 03/21/2014 06:54 AM, Jan Beulich wrote:
>>>>> On 21.03.14 at 04:51, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:
>>> -    /*
>>> -     * Some Solaris PV drivers fail if max > base + 2. Help them out by
>>> -     * hiding the PVRDTSCP leaf if PVRDTSCP is disabled.
>>> -     */
>>> -    limit = (d->arch.tsc_mode < TSC_MODE_PVRDTSCP) ? 2 : 3;
>>> +    /* Number of leaves may be user-specified */
>>> +    domain_cpuid(d, base, 0, &limit, &dummy, &dummy, &dummy);
>>> +    limit &= 0xff;
>>> +    if ( (limit < 2) || (limit > 3) )
>> So all of the sudden you also enforce a lower limit? That doesn't
>> seem to belong here (and at a first glance it doesn't seem to be
>> right either).
>>
>> There are two things you want enforce
>> - limit never becoming zero due to user override (at once taking
>>    care of the no override case)
> 
> You think not having leaf 1 is something we should allow? I can see why
> 2 perhaps may be omitted.

If we force the lower limit that can be asked for to 1, leaf 1 will always
be visible.

Jan


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