linux-kernel - RE: [v3 08/26] iommu, x86: Add intel_irq_remapping

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Date:	Thu, 29 Jan 2015 08:57:54 +0000
From:	"Wu, Feng" <feng.wu@...el.com>
To:	David Woodhouse <dwmw2@...radead.org>
CC:	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
	"gleb@...nel.org" <gleb@...nel.org>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>,
	"joro@...tes.org" <joro@...tes.org>,
	"alex.williamson@...hat.com" <alex.williamson@...hat.com>,
	"jiang.liu@...ux.intel.com" <jiang.liu@...ux.intel.com>,
	"eric.auger@...aro.org" <eric.auger@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"Wu, Feng" <feng.wu@...el.com>
Subject: RE: [v3 08/26] iommu, x86: Add intel_irq_remapping_capability() for
 Intel



> -----Original Message-----
> From: David Woodhouse [mailto:dwmw2@...radead.org]
> Sent: Wednesday, January 28, 2015 11:38 PM
> To: Wu, Feng
> Cc: tglx@...utronix.de; mingo@...hat.com; hpa@...or.com; x86@...nel.org;
> gleb@...nel.org; pbonzini@...hat.com; joro@...tes.org;
> alex.williamson@...hat.com; jiang.liu@...ux.intel.com; eric.auger@...aro.org;
> linux-kernel@...r.kernel.org; iommu@...ts.linux-foundation.org;
> kvm@...r.kernel.org
> Subject: Re: [v3 08/26] iommu, x86: Add intel_irq_remapping_capability() for
> Intel
> 
> On Fri, 2014-12-12 at 23:14 +0800, Feng Wu wrote:
> > Add the Intel side implementation for capability in
> > struct irq_remap_ops.
> >
> > Signed-off-by: Feng Wu <feng.wu@...el.com>
> > Reviewed-by: Jiang Liu <jiang.liu@...ux.intel.com>
> 
> > +static bool intel_irq_remapping_capability(enum irq_remap_cap cap)
> > +{
> > +	struct dmar_drhd_unit *drhd;
> > +	struct intel_iommu *iommu;
> > +
> > +	switch (cap) {
> > +	case IRQ_POSTING_CAP:
> > +		/*
> > +		 * If 1) posted-interrupts is disabled by user
> > +		 * or 2) irq remapping is disabled, posted-interrupts
> > +		 * is not supported.
> > +		 */
> > +		if (disable_irq_post || !irq_remapping_enabled)
> > +			return 0;
> > +
> > +		for_each_iommu(iommu, drhd)
> > +			if (!cap_pi_support(iommu->cap))
> > +				return 0;
> > +
> 
> If a new IOMMU is hotplugged now which doesn't support posted
> interrupts, what happens?

Good question, Just had a offline discussion with Jiang Liu, actually, there
is the same question for IR. In the current implementation, If IR is in use
and a new IOMMU without IR capability is hotplugged, it will reject this
hotplugging. I think I can simple follow the same policy for PI.

Thanks,
Feng

> 
> --
> David Woodhouse                            Open Source Technology
> Centre
> David.Woodhouse@...el.com                              Intel
> Corporation