linux-kernel - [PATCH v2 1/1] iommu/vt-d: Fix missed device TLB cache tag

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Date: Thu, 20 Jun 2024 14:29:40 +0800
From: Lu Baolu <baolu.lu@...ux.intel.com>
To: Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>,
	Kevin Tian <kevin.tian@...el.com>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Jacek Lawrynowicz <jacek.lawrynowicz@...ux.intel.com>
Cc: iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH v2 1/1] iommu/vt-d: Fix missed device TLB cache tag

When a domain is attached to a device, the required cache tags are
assigned to the domain so that the related caches can be flushed
whenever it is needed. The device TLB cache tag is created based
on whether the ats_enabled field of the device's iommu data is set.
This creates an ordered dependency between cache tag assignment and
ATS enabling.

The device TLB cache tag would not be created if device's ATS is
enabled after the cache tag assignment. This causes devices with PCI
ATS support to malfunction.

The ATS control is exclusively owned by the iommu driver. Hence, move
cache_tag_assign_domain() after PCI ATS enabling to make sure that the
device TLB cache tag is created for the domain.

Fixes: 3b1d9e2b2d68 ("iommu/vt-d: Add cache tag assignment interface")
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/intel/iommu.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

Change log:
v2:
- Reverting the order instead of adding unnecessary run-time overhead.

v1:
- https://lore.kernel.org/linux-iommu/20240619015345.182773-1-baolu.lu@linux.intel.com/

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 2e9811bf2a4e..fd11a080380c 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2114,12 +2114,6 @@ static int dmar_domain_attach_device(struct dmar_domain *domain,
 	if (ret)
 		return ret;
 
-	ret = cache_tag_assign_domain(domain, dev, IOMMU_NO_PASID);
-	if (ret) {
-		domain_detach_iommu(domain, iommu);
-		return ret;
-	}
-
 	info->domain = domain;
 	spin_lock_irqsave(&domain->lock, flags);
 	list_add(&info->link, &domain->devices);
@@ -2137,15 +2131,21 @@ static int dmar_domain_attach_device(struct dmar_domain *domain,
 	else
 		ret = intel_pasid_setup_second_level(iommu, domain, dev, IOMMU_NO_PASID);
 
-	if (ret) {
-		device_block_translation(dev);
-		return ret;
-	}
+	if (ret)
+		goto out_block_translation;
 
 	if (sm_supported(info->iommu) || !domain_type_is_si(info->domain))
 		iommu_enable_pci_caps(info);
 
+	ret = cache_tag_assign_domain(domain, dev, IOMMU_NO_PASID);
+	if (ret)
+		goto out_block_translation;
+
 	return 0;
+
+out_block_translation:
+	device_block_translation(dev);
+	return ret;
 }
 
 /**
-- 
2.34.1