linux-kernel - [PATCH v3 6/6] iommu/vt-d: Remove unnecessary checks in iopf disabling path

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Message-Id: <20230324120234.313643-7-baolu.lu@linux.intel.com>
Date:   Fri, 24 Mar 2023 20:02:34 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     iommu@...ts.linux.dev, dmaengine@...r.kernel.org
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Kevin Tian <kevin.tian@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org, Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH v3 6/6] iommu/vt-d: Remove unnecessary checks in iopf disabling path

iommu_unregister_device_fault_handler() and iopf_queue_remove_device()
are called after device has stopped issuing new page falut requests and
all outstanding page requests have been drained. They should never fail.
Trigger a warning if it happens unfortunately.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/intel/iommu.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index cd3a3c4b5e64..c771233d6f2a 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4707,7 +4707,6 @@ static int intel_iommu_disable_iopf(struct device *dev)
 {
 	struct device_domain_info *info = dev_iommu_priv_get(dev);
 	struct intel_iommu *iommu = info->iommu;
-	int ret;
 
 	if (!info->pri_enabled)
 		return -EINVAL;
@@ -4723,15 +4722,15 @@ static int intel_iommu_disable_iopf(struct device *dev)
 	pci_disable_pri(to_pci_dev(dev));
 	info->pri_enabled = 0;
 
-	ret = iommu_unregister_device_fault_handler(dev);
-	if (ret)
-		return ret;
-
-	ret = iopf_queue_remove_device(iommu->iopf_queue, dev);
-	if (ret)
-		iommu_register_device_fault_handler(dev, iommu_queue_iopf, dev);
+	/*
+	 * With PRI disabled and outstanding PRQs drained, unregistering
+	 * fault handler and removing device from iopf queue should never
+	 * fail.
+	 */
+	WARN_ON(iommu_unregister_device_fault_handler(dev));
+	WARN_ON(iopf_queue_remove_device(iommu->iopf_queue, dev));
 
-	return ret;
+	return 0;
 }
 
 static int
-- 
2.34.1