linux-kernel - Re: [PATCH v2 2/2] vsmp: Ignore IOAPIC IRQ affinity if possible

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Message-ID: <20120509212117.GA32594@NoteStation.guest.lab126.com>
Date:	Thu, 10 May 2012 00:21:17 +0300
From:	Ido Yariv <ido@...ery.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	"Shai Fultheim (Shai@...leMP.com)" <Shai@...leMP.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Ravikiran Thirumalai <kiran.thirumalai@...il.com>
Subject: Re: [PATCH v2 2/2] vsmp: Ignore IOAPIC IRQ affinity if possible

Hi Ingo,

On Wed, May 09, 2012 at 11:18:27AM +0200, Ingo Molnar wrote:
> 
> * Shai Fultheim (Shai@...leMP.com) <Shai@...leMP.com> wrote:
> 
> > Ingo Molnar <mingo.kernel.org@...il.com> wrote:
> > > * Ido Yariv <ido@...ery.com> wrote:
> > 
> > > > @@ -51,6 +60,7 @@ void __init default_setup_apic_routing(void)
> > > >  	if (is_vsmp_box()) {
> > > >  		/* need to update phys_pkg_id */
> > > >  		apic->phys_pkg_id = apicid_phys_pkg_id;
> > > > +		apic->vector_allocation_domain =
> > > fill_vector_allocation_domain;
> > > >  	}
> > > >  }
> > > 
> > > This is_vsmp_box() special case should really move into its own
> > > apic handler.
> > > 
> > > Thanks,
> > 
> > Ingo,
> > 
> > vSMP Foundation virtualize multiple systems as one.  The Guest 
> > OS is using the underlying hardware APIC driver, and therefore 
> > we must allow the various APIC drivers to kick in.  When using 
> > vSMP Foundation APIC driver is selected by the kernel based on 
> > the hardware that is being virtualized, and that can be APIC, 
> > X2APIC phys, X2APIC cluster, summit, etc.
> > 
> > If we would to implement an APIC handler, we would not be able 
> > to use the native hardware APIC driver (unless we do an ugly 
> > hack).
> 
> If you need a callback on that level then there's a cleaner 
> mechanism than open-coding vsmp handlers into generic code:
> 
>  - create a new platform callback in x86_platform_ops
>  - call it from apic_64.c if set
>  - fill in the vSMP specific handler from the vSMP init code

Sounds good.

We'll look into it and post an alternative patch to this one.

Thanks,
Ido.
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