linux-kernel - [PATCH v1] iommu/vt-d: Remove redundant SLTS cap check for nested and dirty tracking

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Message-ID: <20250605101052.955174-1-wei.w.wang@intel.com>
Date: Thu,  5 Jun 2025 18:10:52 +0800
From: Wei Wang <wei.w.wang@...el.com>
To: baolu.lu@...ux.intel.com,
	kevin.tian@...el.com,
	yi.l.liu@...el.com,
	jgg@...dia.com,
	dwmw2@...radead.org,
	joro@...tes.org,
	linux-kernel@...r.kernel.org,
	iommu@...ts.linux.dev
Cc: Wei Wang <wei.w.wang@...el.com>
Subject: [PATCH v1] iommu/vt-d: Remove redundant SLTS cap check for nested and dirty tracking

In intel_iommu_domain_alloc_paging_flags():
For the nested_parent case, nested_supported() has been check earlier,
and for the dirty_tracking case, ssads_supported() has been check earlier.
Both of these imply SLTS support, making the subsequent SLTS cap check
redundant.
Also, false-initialize the first_stage boolean to simplify the code.

Signed-off-by: Wei Wang <wei.w.wang@...el.com>
---
 drivers/iommu/intel/iommu.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 7aa3932251b2..a79f91b47a8a 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -3340,7 +3340,7 @@ intel_iommu_domain_alloc_paging_flags(struct device *dev, u32 flags,
 	struct intel_iommu *iommu = info->iommu;
 	struct dmar_domain *dmar_domain;
 	struct iommu_domain *domain;
-	bool first_stage;
+	bool first_stage = false;
 
 	if (flags &
 	    (~(IOMMU_HWPT_ALLOC_NEST_PARENT | IOMMU_HWPT_ALLOC_DIRTY_TRACKING |
@@ -3356,13 +3356,8 @@ intel_iommu_domain_alloc_paging_flags(struct device *dev, u32 flags,
 	 * IOMMU_HWPT_ALLOC_NEST_PARENT or IOMMU_HWPT_ALLOC_DIRTY_TRACKING
 	 * is specified.
 	 */
-	if (nested_parent || dirty_tracking) {
-		if (!sm_supported(iommu) || !ecap_slts(iommu->ecap))
-			return ERR_PTR(-EOPNOTSUPP);
-		first_stage = false;
-	} else {
+	if (!nested_parent && !dirty_tracking)
 		first_stage = first_level_by_default(iommu);
-	}
 
 	dmar_domain = paging_domain_alloc(dev, first_stage);
 	if (IS_ERR(dmar_domain))

base-commit: 16b70698aa3ae7888826d0c84567c72241cf6713
-- 
2.43.0