Re: [Xen-devel] [v4] libxc: Expose the 1GB pages cpuid flag to guest

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

Andrew Cooper wrote on 2014-12-04:
> On 04/12/14 01:50, Zhang, Yang Z wrote:
>> Konrad Rzeszutek Wilk wrote on 2014-12-03:
>>> On Wed, Dec 03, 2014 at 09:38:49AM +0000, Ian Campbell wrote:
>>>> On Tue, 2014-12-02 at 16:09 -0500, Konrad Rzeszutek Wilk wrote:
>>>>> On Fri, Nov 28, 2014 at 11:50:43AM +0000, Ian Campbell wrote:
>>>>>> On Fri, 2014-11-28 at 18:52 +0800, Liang Li wrote:
>>>>>>> If hardware support the 1GB pages, expose the feature to guest
>>>>>>> by default. Users don't have to use a 'cpuid= ' option in
>>>>>>> config fil e to turn it on.
>>>>>>> 
>>>>>>> If guest use shadow mode, the 1GB pages feature will be hidden
>>>>>>> from guest, this is done in the function hvm_cpuid(). So the
>>>>>>> change is okay for shadow mode case.
>>>>>>> 
>>>>>>> Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
>>>>>>> Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>>>>>> FTR although this is strictly speaking a toolstack patch I think
>>>>>> the main ack required should be from the x86 hypervisor guys...
>>>>> Jan acked it.
>>>> For 4.5? Probably not. Have you release acked it? No. This seemed
>>>> like 4.6 material to me, or at least I've not seen any
>>>> mention/argument to the contrary.
>>> Correct. 4.6 please.
>> I think this more like a bug fixing than a feature. See our previous 
>> discussion.
> 
> It is allowing HVM guests to use a brand new hardware feature which
> was previously unavailable to them.

Actually, we have regular test case to cover 1G page size which exposing the 1G 
feature manually through config file. And we also have a bug to track this 
issue. So it more likes a bugfix to me. But you are right. It is a new feature 
from guest's point.

> 
> It is absolutely not a bugfix, and not appropriate for 4.5 at this
> point, but a good candidate for acceptance as soon as the 4.6 dev window 
> opens.

Agree.

> 
> ~Andrew


Best regards,
Yang


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