[v6 7/8] iommu, x86: define irq_remapping_cap()

[Feng Wu <feng.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

This patch adds a new interface irq_remapping_cap() to detect
whether irq remapping supports new features, such as VT-d
Posted-Interrupts. We export this function out, so that KVM
code can check this and use this mechanism properly.

Signed-off-by: Feng Wu <feng.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Reviewed-by: Jiang Liu <jiang.liu-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
---
 arch/x86/include/asm/irq_remapping.h | 2 ++
 drivers/iommu/irq_remapping.c        | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/arch/x86/include/asm/irq_remapping.h b/arch/x86/include/asm/irq_remapping.h
index 202e040..61aa8ad 100644
--- a/arch/x86/include/asm/irq_remapping.h
+++ b/arch/x86/include/asm/irq_remapping.h
@@ -35,6 +35,7 @@ enum irq_remap_cap {
 	IRQ_POSTING_CAP = 0,
 };
 
+extern bool irq_remapping_cap(enum irq_remap_cap cap);
 extern void set_irq_remapping_broken(void);
 extern int irq_remapping_prepare(void);
 extern int irq_remapping_enable(void);
@@ -64,6 +65,7 @@ struct vcpu_data {
 
 #else  /* CONFIG_IRQ_REMAP */
 
+static bool irq_remapping_cap(enum irq_remap_cap cap) { return 0; }
 static inline void set_irq_remapping_broken(void) { }
 static inline int irq_remapping_prepare(void) { return -ENODEV; }
 static inline int irq_remapping_enable(void) { return -ENODEV; }
diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
index ed605a9..2d99930 100644
--- a/drivers/iommu/irq_remapping.c
+++ b/drivers/iommu/irq_remapping.c
@@ -81,6 +81,15 @@ void set_irq_remapping_broken(void)
 	irq_remap_broken = 1;
 }
 
+bool irq_remapping_cap(enum irq_remap_cap cap)
+{
+	if (!remap_ops || disable_irq_post)
+		return 0;
+
+	return (remap_ops->capability & (1 << cap));
+}
+EXPORT_SYMBOL_GPL(irq_remapping_cap);
+
 int __init irq_remapping_prepare(void)
 {
 	if (disable_irq_remap)
-- 
2.1.0