linux-kernel - RE: [v8 3/9] iommu, x86: Implement irq_set_vcpu_affinity for intel_ir

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Date:	Wed, 3 Jun 2015 01:05:24 +0000
From:	"Wu, Feng" <feng.wu@...el.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	"joro@...tes.org" <joro@...tes.org>,
	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"jiang.liu@...ux.intel.com" <jiang.liu@...ux.intel.com>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Wu, Feng" <feng.wu@...el.com>
Subject: RE: [v8 3/9] iommu, x86: Implement irq_set_vcpu_affinity for
 intel_ir_chip



> -----Original Message-----
> From: Thomas Gleixner [mailto:tglx@...utronix.de]
> Sent: Tuesday, June 02, 2015 9:59 PM
> To: Wu, Feng
> Cc: joro@...tes.org; dwmw2@...radead.org; jiang.liu@...ux.intel.com;
> iommu@...ts.linux-foundation.org; linux-kernel@...r.kernel.org
> Subject: Re: [v8 3/9] iommu, x86: Implement irq_set_vcpu_affinity for
> intel_ir_chip
> 
> On Wed, 27 May 2015, Feng Wu wrote:
> > +	/* stop posting interrupts, back to remapping mode */
> > +	if (!vcpu_info) {
> > +		modify_irte(&ir_data->irq_2_iommu, &ir_data->irte_entry);
> > +	} else {
> > +		vcpu_pi_info = (struct vcpu_data *)vcpu_info;
> > +
> > +		/*
> > +		 * "ir_data->irte_entry" saves the remapped format of IRTE,
> > +		 * which being a cached irte is still updated when setting
> > +		 * the affinity even when we are in posted mode. So this make
> 
> s/make/makes/
> 
> > +		 * it possible to switch back to remapped mode from posted mode,
> > +		 * we can just set "ir_data->irte_entry" to hardware for that
> > +		 * purpose. Here we store the posted format of IRTE in another
> > +		 * new member "ir_data->irte_pi_entry" to not corrupt
> 
> Remove the 'another new member' please. That member is not longer new
> once that patch is applied.
> 
> Now there is another question. Are we actually using that pi_entry
> cached value for anything else than this code here? If not, we can do
> this on the stack and avoid the extra storage in ir_data.
> 

That's a good comments. I also thought about this before. Right now the cached value
is only used here in this function, but I am not sure whether we need it in future. Anyway,
I think we can delete it now.

Thanks,
Feng


> Thanks,
> 
> 	tglx
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