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    SubjectRE: [v3 08/26] iommu, x86: Add intel_irq_remapping_capability() for Intel
    Date


    > -----Original Message-----
    > From: David Woodhouse [mailto:dwmw2@infradead.org]
    > Sent: Wednesday, January 28, 2015 11:38 PM
    > To: Wu, Feng
    > Cc: tglx@linutronix.de; mingo@redhat.com; hpa@zytor.com; x86@kernel.org;
    > gleb@kernel.org; pbonzini@redhat.com; joro@8bytes.org;
    > alex.williamson@redhat.com; jiang.liu@linux.intel.com; eric.auger@linaro.org;
    > linux-kernel@vger.kernel.org; iommu@lists.linux-foundation.org;
    > kvm@vger.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@intel.com>
    > > Reviewed-by: Jiang Liu <jiang.liu@linux.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@intel.com Intel
    > Corporation
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