linux-kernel - [PATCH v4 3/4] iommu/vt-d: Remove domain_update_iommu

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Date:   Sun,  8 May 2022 20:35:24 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>, Jason Gunthorpe <jgg@...dia.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>
Cc:     Jacob jun Pan <jacob.jun.pan@...el.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH v4 3/4] iommu/vt-d: Remove domain_update_iommu_snooping()

The IOMMU force snooping capability is not required to be consistent
among all the IOMMUs anymore. Remove force snooping capability check
in the IOMMU hot-add path and domain_update_iommu_snooping() becomes
a dead code now.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
Reviewed-by: Kevin Tian <kevin.tian@...el.com>
---
 drivers/iommu/intel/iommu.c | 34 +---------------------------------
 1 file changed, 1 insertion(+), 33 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 048ebfbd5fcb..444d51a18c93 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -533,33 +533,6 @@ static void domain_update_iommu_coherency(struct dmar_domain *domain)
 	rcu_read_unlock();
 }
 
-static bool domain_update_iommu_snooping(struct intel_iommu *skip)
-{
-	struct dmar_drhd_unit *drhd;
-	struct intel_iommu *iommu;
-	bool ret = true;
-
-	rcu_read_lock();
-	for_each_active_iommu(iommu, drhd) {
-		if (iommu != skip) {
-			/*
-			 * If the hardware is operating in the scalable mode,
-			 * the snooping control is always supported since we
-			 * always set PASID-table-entry.PGSNP bit if the domain
-			 * is managed outside (UNMANAGED).
-			 */
-			if (!sm_supported(iommu) &&
-			    !ecap_sc_support(iommu->ecap)) {
-				ret = false;
-				break;
-			}
-		}
-	}
-	rcu_read_unlock();
-
-	return ret;
-}
-
 static int domain_update_iommu_superpage(struct dmar_domain *domain,
 					 struct intel_iommu *skip)
 {
@@ -3606,12 +3579,7 @@ static int intel_iommu_add(struct dmar_drhd_unit *dmaru)
 			iommu->name);
 		return -ENXIO;
 	}
-	if (!ecap_sc_support(iommu->ecap) &&
-	    domain_update_iommu_snooping(iommu)) {
-		pr_warn("%s: Doesn't support snooping.\n",
-			iommu->name);
-		return -ENXIO;
-	}
+
 	sp = domain_update_iommu_superpage(NULL, iommu) - 1;
 	if (sp >= 0 && !(cap_super_page_val(iommu->cap) & (1 << sp))) {
 		pr_warn("%s: Doesn't support large page.\n",
-- 
2.25.1