linux-kernel - [PATCH] x86/iommu: Fix two minimal issues in check_iommu

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Date:   Wed, 23 Dec 2020 14:24:12 +0800
From:   Zhenzhong Duan <zhenzhong.duan@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     zhongjiang@...wei.com, joe@...ches.com, konrad.wilk@...cle.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        iommu@...ts.linux-foundation.org, dwmw2@...radead.org,
        baolu.lu@...ux.intel.com, joro@...tes.org, will@...nel.org,
        Zhenzhong Duan <zhenzhong.duan@...il.com>
Subject: [PATCH] x86/iommu: Fix two minimal issues in check_iommu_entries()

check_iommu_entries() checks for cyclic dependency in iommu entries
and fixes the cyclic dependency by setting x->depend to NULL. But
this repairing isn't correct if q is in front of p, there will be
"EXECUTION ORDER INVALID!" report following. Fix it by NULLing
whichever in the front.

The second issue is about the report of exectuion order reverse,
the order is reversed incorrectly in the report, fix it.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...il.com>
---
 arch/x86/kernel/pci-iommu_table.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/pci-iommu_table.c b/arch/x86/kernel/pci-iommu_table.c
index 2e9006c..40c8249 100644
--- a/arch/x86/kernel/pci-iommu_table.c
+++ b/arch/x86/kernel/pci-iommu_table.c
@@ -60,7 +60,10 @@ void __init check_iommu_entries(struct iommu_table_entry *start,
 			printk(KERN_ERR "CYCLIC DEPENDENCY FOUND! %pS depends on %pS and vice-versa. BREAKING IT.\n",
 			       p->detect, q->detect);
 			/* Heavy handed way..*/
-			x->depend = NULL;
+			if (p > q)
+				q->depend = NULL;
+			else
+				p->depend = NULL;
 		}
 	}
 
@@ -68,7 +71,7 @@ void __init check_iommu_entries(struct iommu_table_entry *start,
 		q = find_dependents_of(p, finish, p);
 		if (q && q > p) {
 			printk(KERN_ERR "EXECUTION ORDER INVALID! %pS should be called before %pS!\n",
-			       p->detect, q->detect);
+			       q->detect, p->detect);
 		}
 	}
 }
-- 
1.8.3.1