> -----Original Message-----
> From: Zhang, Yang Z
> Sent: Thursday, December 18, 2014 10:26 PM
> To: Wu, Feng; t...@linutronix.de; mi...@redhat.com; h...@zytor.com;
> x...@kernel.org; g...@kernel.org; pbonz...@redhat.com;
> dw...@infradead.org; j...@8bytes.org; alex.william...@redhat.com;
> jiang....@linux.intel.com
> Cc: eric.au...@linaro.org; linux-ker...@vger.kernel.org;
> io...@lists.linux-foundation.org; kvm@vger.kernel.org; Wu, Feng
> Subject: RE: [v3 06/26] iommu, x86: No need to migrating irq for VT-d
> Posted-Interrupts
>
> Feng Wu wrote on 2014-12-12:
> > We don't need to migrate the irqs for VT-d Posted-Interrupts here.
> > When 'pst' is set in IRTE, the associated irq will be posted to guests
> > instead of interrupt remapping. The destination of the interrupt is
> > set in Posted-Interrupts Descriptor, and the migration happens during
> > vCPU scheduling.
> >
> > However, we still update the cached irte here, which can be used when
> > changing back to remapping mode.
> >
> > Signed-off-by: Feng Wu <feng...@intel.com>
> > Reviewed-by: Jiang Liu <jiang....@linux.intel.com>
> > ---
> > drivers/iommu/intel_irq_remapping.c | 6 +++++-
> > 1 file changed, 5 insertions(+), 1 deletion(-)
> > diff --git a/drivers/iommu/intel_irq_remapping.c
> > b/drivers/iommu/intel_irq_remapping.c index 48c2051..ab9057a 100644 ---
> > a/drivers/iommu/intel_irq_remapping.c +++
> > b/drivers/iommu/intel_irq_remapping.c @@ -977,6 +977,7 @@
> > intel_ir_set_affinity(struct irq_data *data, const struct cpumask *mask,
> > {
> > struct intel_ir_data *ir_data = data->chip_data; struct irte
> > *irte =
> > &ir_data->irte_entry; + struct irte_pi *irte_pi = (struct irte_pi
> > *)irte; struct irq_cfg *cfg = irqd_cfg(data); struct irq_data *parent
> > = data->parent_data; int ret;
> > @@ -991,7 +992,10 @@ intel_ir_set_affinity(struct irq_data *data,
> > const struct cpumask *mask,
> > */
> > irte->vector = cfg->vector;
> > irte->dest_id = IRTE_DEST(cfg->dest_apicid);
> > - modify_irte(&ir_data->irq_2_iommu, irte);
> > +
> > + /* We don't need to modify irte if the interrupt is for posting. */
> > + if (irte_pi->pst != 1)
> > + modify_irte(&ir_data->irq_2_iommu, irte);
>
> What happens if user changes the IRQ affinity manually?
If the IRQ is posted, its affinity is controlled by guest (irq <---> vCPU
<----> pCPU),
it has no effect when host changes its affinity.
Thanks,
Feng
>
> >
> > /*
> > * After this point, all the interrupts will start arriving
>
>
> Best regards,
> Yang
>
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