Re: [PATCH v7 1/3] xen/libxc: Allow changing max number of hypervisor cpuid leaves

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 03/27/2014 09:13 AM, Ian Campbell wrote:
> On Mon, 2014-03-24 at 19:18 -0400, Boris Ostrovsky wrote:
>> Add support for changing max number of hypervisor leaves from configuration
>> file.
>>
>> This number can be specified using xl's standard 'cpuid' option. Only lowest
>> 8 bits of leaf's 0x4000xx00 eax register are processed, all others are ignored.
> This sounds like it would need a docs update to go along with it, both
> to address this specific constraint and perhaps to give an example of
> the syntax (unless it is already obvious?).

This could to xl.cfg.5[.txt|.html], something in the cpuid option 
description. E.g.

   Note: when specifying CPUID for hypervisor leaves (0x4000xxxx major
   group) only the lowest 8 bits of leaf's 0x4000xx00 EAX register that 
signify
   maximum number of hypervisor leaves are processed, the rest are ignored.

As for example, this uses the same syntax as all other leaves so I am 
not sure
anything more is needed.


> Speaking of obvious syntaxes, does the list in libxl_cpuid_parse_config
> want updating so people can use maxhvleaf=2 instead of whatever the more
> obscure syntax would be?

Yes, I should add this.

Thanks.
-boris