Re: [PATCH v3 5/5] OvmfPkg/SmmCpuFeaturesLib: Skip SMBASE configuration

["Gerd Hoffmann" <kraxel@redhat.com>]

On Sun, Jan 29, 2023 at 05:47:00AM +0000, Wu, Jiaxin wrote:
> > 
> >  * Why do you want do it in PEI instead?  The cover letter claims this
> >    improves boot performance.  I don't buy that.  You are not skipping
> >    the relocation process, you are just doing it somewhere else.
> 
> I clarified why it can improves boot performance, it's not just do
> somewhere else, but also each cpus smbase can be programmed in
> parallel. See [PATCH v3 3/5] UefiCpuPkg/PiSmmCpuDxeSmm: Consume SMM
> Base Hob for SmBase info:

Current state:

 * PiSmmCpuDxeSmm does SMM initialization, including programming SMBASE,
   serialized.

With this series applied:

 * Some PEI module programs SMBASE, serialized.
 * PiSmmCpuDxeSmm does SMM initialization, but NOT programming SMBASE,
   in parallel.

Sure PiSmmCpuDxeSmm alone will run faster because it can run parallel
now.

But the serialized SMBASE programming still happens, now in the PEI
module, and I don't see a good reason why the runtime the new PEI module
and the runtime of PiSmmCpuDxeSmm combined is faster than before.

> >  * Where is the code?
> See the design of existing function: SemaphoreHook (Index, &mRebased[Index]); 

I mean the PEI module code.

> >  * It is totally unclear whenever it is possible and/or useful to
> >    initialize SMM that way on OVMF.

> Add the same handing logic code in OVMF is necessary to make sure it
> work. If someone produced such hob in OVMF platform,

Do you intent submitting code for OVMF producing such a HOB?
There isn't any in this series.

> Changes in OVMF is make sure it runs into right way.

As it stands you are only adding dead code for no reason.

How is the SMM initialization of hotplugged CPUs
supposed to work with the new mode of operation?

take care,
  Gerd