[PATCH 1/2] iommu/vt-d: Avoid unnecessary global IRTE cache invalidation

[Lu Baolu]

Some VT-d hardware implementations invalidate all interrupt remapping
hardware translation caches as part of SIRTP flow. The VT-d spec adds
a ESIRTPS (Enhanced Set Interrupt Remap Table Pointer Support, section
11.4.2 in VT-d spec) capability bit to indicate this. With this bit set,
software has no need to issue the global invalidation request.

Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/iommu/intel/iommu.h         | 1 +
 drivers/iommu/intel/irq_remapping.c | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
index eef1a166b855..5407d82df4d1 100644
--- a/drivers/iommu/intel/iommu.h
+++ b/drivers/iommu/intel/iommu.h
@@ -146,6 +146,7 @@
 /*
  * Decoding Capability Register
  */
+#define cap_esirtps(c)		(((c) >> 62) & 1)
 #define cap_fl5lp_support(c)	(((c) >> 60) & 1)
 #define cap_pi_support(c)	(((c) >> 59) & 1)
 #define cap_fl1gp_support(c)	(((c) >> 56) & 1)
diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c
index 2e9683e970f8..b4a91fbd1c2f 100644
--- a/drivers/iommu/intel/irq_remapping.c
+++ b/drivers/iommu/intel/irq_remapping.c
@@ -494,7 +494,8 @@ static void iommu_set_irq_remapping(struct intel_iommu *iommu, int mode)
 	 * Global invalidation of interrupt entry cache to make sure the
 	 * hardware uses the new irq remapping table.
 	 */
-	qi_global_iec(iommu);
+	if (!cap_esirtps(iommu->cap))
+		qi_global_iec(iommu);
 }
 
 static void iommu_enable_irq_remapping(struct intel_iommu *iommu)
-- 
2.34.1