Re: [Xen-devel] lock in vhpet

[Keir Fraser <keir@xxxxxxx>]

On 18/04/2012 10:14, "Keir Fraser" <keir@xxxxxxx> wrote:

> On 18/04/2012 09:29, "Keir Fraser" <keir@xxxxxxx> wrote:
> 
>> On 18/04/2012 08:55, "Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx> wrote:
>> 
>>>> If the HPET accesses are atomic on bare metal, we have to maintain that,
>>>> even
>>>> if some guests have extra locking themselves. Also, in some cases Xen needs
>>>> locking to correctly maintain its own internal state regardless of what an
>>>> (untrusted) guest might do. So we cannot just get rid of the vhpet lock
>>>> everywhere. It's definitely not correct to do so. Optimising the hpet read
>>>> path
>>>> however, sounds okay. I agree the lock may not be needed on that specific
>>>> path.
>>> 
>>> You are right.
>>> For this case, since the main access of hpet is to read the main counter, so
>>> I
>>> think the rwlock is a better choice.
>> 
>> I'll see if I can make a patch...
> 
> Please try the attached patch (build tested only).

Actually try this updated one. :-)

>  -- Keir
> 
>>  -- Keir
>> 
>> 
>

Attachment: 00-hpet-lockfree-v2
Description: Binary data

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel