Re: [Qemu-devel] [PATCH V14 2/7] Add TPM (frontend) hardware interface (TPM TIS) to Qemu

[Stefan Berger <stefanb@linux.vnet.ibm.com>]

On 02/21/2012 11:34 PM, Michael S. Tsirkin wrote:
> On Tue, Feb 21, 2012 at 07:21:28PM -0500, Stefan Berger wrote:
>> On 02/21/2012 06:08 PM, Michael S. Tsirkin wrote:
>>
>
>> The locking times are short since no major computations
>> are done while the lock is held.
>> Considering that the TPM TIS interface is a non-DMA, byte-by-byte
>> send/receive interface, the performance problems, if at all a
>> problem, are to be found somewhere else : VMExits for example; if
>> interface is used in polling mode, then the interval between polls.
>>
>>     Stefan
> In that case, you can take the qemu lock in your backend
> and avoid locking in the frontend completely.
>
Maybe it's just me, but I prefer to have locks around the code that has 
the criticial section, rather than entering a function with locks held, 
especially since it would be in a different file (backend) where the 
lock then is grabbed.
Also I do need a lock in the frontend for the condition that is used there.

     Stefan