linux-kernel - [PATCH 5/6] iommu/vt-d: Avoid unnecessary global IRTE cache invalidation

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Date:   Mon, 26 Sep 2022 21:15:28 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: [PATCH 5/6] iommu/vt-d: Avoid unnecessary global IRTE cache invalidation

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.

The spec also states in 11.4.4 that hardware also performs global
invalidation on all interrupt remapping caches as part of Interrupt
Remapping Disable operation if ESIRTPS capability bit is set.

This checks the ESIRTPS capability bit and skip software global cache
invalidation if it's set.

Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>
Reviewed-by: Kevin Tian <kevin.tian@...el.com>
Link: https://lore.kernel.org/r/20220921065741.3572495-1-baolu.lu@linux.intel.com
---
 drivers/iommu/intel/iommu.h         | 1 +
 drivers/iommu/intel/irq_remapping.c | 6 ++++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
index 99cc75ecac63..bddf6c69587d 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..5962bb5027d0 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)
@@ -680,7 +681,8 @@ static void iommu_disable_irq_remapping(struct intel_iommu *iommu)
 	 * global invalidation of interrupt entry cache before disabling
 	 * interrupt-remapping.
 	 */
-	qi_global_iec(iommu);
+	if (!cap_esirtps(iommu->cap))
+		qi_global_iec(iommu);
 
 	raw_spin_lock_irqsave(&iommu->register_lock, flags);
 
-- 
2.34.1