Re: [Xen-devel] [PATCH 3/8] ACPI: processor: add __acpi_processor_[un]register_driver helpers.

From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: Konrad Rzeszutek Wilk <konrad@darnok.org>,
	"jeremy@goop.org" <jeremy@goop.org>,
	"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
	"Ian.Campbell@citrix.com" <Ian.Campbell@citrix.com>,
	"mike.mcclurg@citrix.com" <mike.mcclurg@citrix.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"stefan.bader@canonical.com" <stefan.bader@canonical.com>,
	"rjw@sisk.pl" <rjw@sisk.pl>,
	"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
	"liang.tang@oracle.com" <liang.tang@oracle.com>,
	"Yu, Ke" <ke.yu@intel.com>,
	"konrad@kernel.org" <konrad@kernel.org>,
	"lenb@kernel.org" <lenb@kernel.org>
Subject: Re: [Xen-devel] [PATCH 3/8] ACPI: processor: add __acpi_processor_[un]register_driver helpers.
Date: Tue, 3 Jan 2012 15:59:25 -0500	[thread overview]
Message-ID: <20120103205925.GI17472@phenom.dumpdata.com> (raw)
In-Reply-To: <AADFC41AFE54684AB9EE6CBC0274A5D10145B9@SHSMSX102.ccr.corp.intel.com>

On Mon, Dec 26, 2011 at 01:31:45AM +0000, Tian, Kevin wrote:
> > From: Konrad Rzeszutek Wilk [mailto:konrad@darnok.org]
> > Sent: Friday, December 23, 2011 11:01 AM
> > 
> > > > OK. Lets put the # VCPU != PCPU aside. Say dom0 will boot with all
> > > > CPUs and then later on the admin starts unplugging them.
> > >
> > > This should be communicated to major Xen based distributions, so that it's
> > > an agreed approach since in majority case dom0 is configured as UP or
> > > a few VCPUs.
> > 
> > I am not saying that is it the agreed approach. There has to be
> > flexibility in supporting both. But what I want to understand whether
> > the requirement for VCPU != PCPU can be put aside and put in the drivers
> > later on.
> 
> sure. VCPU!=PCPU requirement is orthogonal to the basic part for gearing
> ACPI information to Xen.
> 
> > 
> > So that the first approach is not changing the generic drivers (much).
> > The reason I am asking about this is two-fold:
> >  1). For new distros (Ubuntu, Fedora), the default is all VCPUs.
> 
> good to know that.
> 
> >      Enterprising users might use dom0_max_vcpus to limit the VCPU count,
> >      but most won't.
> >      Which mean we can concentrate on bringing the _Pxx/_Cxx parsing
> >      up to the hypervisor. Which is really neccessary on any chipset
> >      which has the notion of TurboBoost (otherwise the Xen scheduler
> >      won't pick this up and won't engage this mode in certain
> >      workloads).
> >  2). The ACPI maintainers are busy with ACPI 5.0. I don't know how
> >      much work this is, but it probably means tons of stuff with
> >      embedded platforms and tons of regression testing. So if there
> >      is a patch that does not impact the generic code much (or any)
> >      it will make their life easier. Which also means we can built
> >      on top that for the VCPU != PCPU case.
> > 
> > That is what I am trying to understand.
> 
> no problem. this incremental approach should work.

Excellent. So now the big question  - is this something you would have the
time to do?