Re: [Qemu-devel] [PATCH v3 for-2.11 1/3] tpm_emulator: Add a caching layer for the TPM Established flag

["Valluri, Amarnath" <amarnath.valluri@intel.com>]

On Wed, 2017-11-15 at 04:47 +0100, Marc-André Lureau wrote:
> Hi
> 
> On Wed, Nov 15, 2017 at 2:16 AM, Stefan Berger
> <stefanb@linux.vnet.ibm.com> wrote:
> > 
> > On 11/14/2017 06:40 PM, Marc-André Lureau wrote:
> > > 
> > > 
> > > Hi
> > > 
> > > On Tue, Nov 14, 2017 at 10:52 PM, Stefan Berger
> > > <stefanb@linux.vnet.ibm.com> wrote:
> > > > 
> > > > 
> > > > Add a caching layer for the TPM established flag so that we
> > > > don't
> > > > need to go to the emulator every time the flag is read by
> > > > accessing
> > > > the REG_ACCESS register.
> > > What's the impact? Isn't this just a "small" optimization? Iotw,
> > > why
> > > is this for-2.11?
> > 
> > The TIS has a register that contains this flag and that's being
> > polled quite
> > frequently. So it generates a lot of traffic to the emulator. This
> > caching
> > layer gets rid of most of the traffic.
> I didn't notice any problem when doing my tests, I guess Amarnath
> niether. perhaps it's best to delay for after 2.11.

Yes, I could see there is little frequent(21 calls to backend) to get
establish flag, and this patch will help to avoid them. But i still
agree with Marc and tag this as "small" optimization.

- Amarnath