linux-kernel - [PATCH 4/8] iommu/vt-d: Remove treatment for revoking PASIDs with pending page faults

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Date: Tue, 27 Feb 2024 10:14:37 +0800
From: Lu Baolu <baolu.lu@...ux.intel.com>
To: Joerg Roedel <joro@...tes.org>
Cc: Tina Zhang <tina.zhang@...el.com>,
	Erick Archer <erick.archer@....com>,
	Jingqi Liu <Jingqi.liu@...el.com>,
	iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/8] iommu/vt-d: Remove treatment for revoking PASIDs with pending page faults

From: Tina Zhang <tina.zhang@...el.com>

Commit 2f26e0a9c986 ("iommu/vt-d: Add basic SVM PASID support") added a
special treatment to mandate that no page faults may be outstanding for
the PASID after intel_svm_unbind_mm() is called, as the PASID will be
released and reused after unbind.

This is unnecessary anymore as no outstanding page faults have been
ensured in the driver's remove_dev_pasid path:

- Tear down the pasid entry, which guarantees that new page faults for
  the PASID will be rejected by the iommu hardware.
- All outstanding page faults have been responded to.
- All hardware pending faults are drained in intel_drain_pasid_prq().

Remove this unnecessary code.

Signed-off-by: Tina Zhang <tina.zhang@...el.com>
Link: https://lore.kernel.org/r/20240219125723.1645703-2-tina.zhang@intel.com
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/intel/svm.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 40edd282903f..a815362c8e60 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -408,13 +408,6 @@ void intel_svm_remove_dev_pasid(struct device *dev, u32 pasid)
 			if (svm->notifier.ops)
 				mmu_notifier_unregister(&svm->notifier, mm);
 			pasid_private_remove(svm->pasid);
-			/*
-			 * We mandate that no page faults may be outstanding
-			 * for the PASID when intel_svm_unbind_mm() is called.
-			 * If that is not obeyed, subtle errors will happen.
-			 * Let's make them less subtle...
-			 */
-			memset(svm, 0x6b, sizeof(*svm));
 			kfree(svm);
 		}
 	}
-- 
2.34.1