iommu, x86: Save the mode (posted or remapped) of an IRTE

Add a new field to struct irq_2_iommu, which captures whether the
associated IRTE is in posted mode or remapped mode. We update this
field when the IRTE is written into the table.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Feng Wu <feng.wu@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Joerg Roedel <joro@8bytes.org>
Cc: jiang.liu@linux.intel.com
Cc: iommu@lists.linux-foundation.org
Cc: dwmw2@infradead.org
Link: http://lkml.kernel.org/r/1433827237-3382-6-git-send-email-feng.wu@intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/iommu/intel_irq_remapping.c

@@ -18,6 +18,11 @@
 
 #include "irq_remapping.h"
 
+enum irq_mode {
+	IRQ_REMAPPING,
+	IRQ_POSTING,
+};
+
 struct ioapic_scope {
 	struct intel_iommu *iommu;
 	unsigned int id;
@@ -37,6 +42,7 @@ struct irq_2_iommu {
 	u16 irte_index;
 	u16 sub_handle;
 	u8  irte_mask;
+	enum irq_mode mode;
 };
 
 struct intel_ir_data {
@@ -104,6 +110,7 @@ static int alloc_irte(struct intel_iommu *iommu, int irq,
 		irq_iommu->irte_index =  index;
 		irq_iommu->sub_handle = 0;
 		irq_iommu->irte_mask = mask;
+		irq_iommu->mode = IRQ_REMAPPING;
 	}
 	raw_spin_unlock_irqrestore(&irq_2_ir_lock, flags);
 
@@ -144,6 +151,9 @@ static int modify_irte(struct irq_2_iommu *irq_iommu,
 	__iommu_flush_cache(iommu, irte, sizeof(*irte));
 
 	rc = qi_flush_iec(iommu, index, 0);
+
+	/* Update iommu mode according to the IRTE mode */
+	irq_iommu->mode = irte->pst ? IRQ_POSTING : IRQ_REMAPPING;
 	raw_spin_unlock_irqrestore(&irq_2_ir_lock, flags);
 
 	return rc;