linux-kernel - [PATCH 12/13] iommu/vt-d: No need to migrating irq for VT-d Posted-Interrtups

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Date:	Mon, 10 Nov 2014 14:26:51 +0800
From:	Feng Wu <feng.wu@...el.com>
To:	gleb@...nel.org, pbonzini@...hat.com, dwmw2@...radead.org,
	joro@...tes.org, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org
Cc:	kvm@...r.kernel.org, iommu@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, Feng Wu <feng.wu@...el.com>
Subject: [PATCH 12/13] iommu/vt-d: No need to migrating irq for VT-d Posted-Interrtups

We don't need to migrate the irqs for VT-d Posted-Interrtups 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.

Signed-off-by: Feng Wu <feng.wu@...el.com>
---
 drivers/iommu/intel_irq_remapping.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
index 87c02fe..249e2b1 100644
--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -1038,6 +1038,13 @@ intel_ioapic_set_affinity(struct irq_data *data, const struct cpumask *mask,
 	if (get_irte(irq, &irte))
 		return -EBUSY;
 
+	/*
+	 * If the interrupt is for posting, it is used by guests,
+	 * we cannot change IRTE here.
+	 */
+	if (irte.irq_post_low.pst == 1)
+		return 0;
+
 	err = assign_irq_vector(irq, cfg, mask);
 	if (err)
 		return err;
-- 
1.7.1

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