From 28ffabf65e42c26b2d7be385ef1941930346d9f9 Mon Sep 17 00:00:00 2001
From: Amol Grover <frextrite@gmail.com>
Date: Sun, 23 Feb 2020 22:25:39 +0530
Subject: [PATCH] iommu/vt-d: Fix RCU list debugging warnings
commit 02d715b4a8182f4887d82df82a7b83aced647760 upstream.
dmar_drhd_units is traversed using list_for_each_entry_rcu()
outside of an RCU read side critical section but under the
protection of dmar_global_lock. Hence add corresponding lockdep
expression to silence the following false-positive warnings:
[ 1.603975] =============================
[ 1.603976] WARNING: suspicious RCU usage
[ 1.603977] 5.5.4-stable #17 Not tainted
[ 1.603978] -----------------------------
[ 1.603980] drivers/iommu/intel-iommu.c:4769 RCU-list traversed in non-reader section!!
[ 1.603869] =============================
[ 1.603870] WARNING: suspicious RCU usage
[ 1.603872] 5.5.4-stable #17 Not tainted
[ 1.603874] -----------------------------
[ 1.603875] drivers/iommu/dmar.c:293 RCU-list traversed in non-reader section!!
Tested-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Signed-off-by: Amol Grover <frextrite@gmail.com>
Cc: stable@vger.kernel.org
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/dmar.h | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index a7cf3599d9a1c..d3ea390336f39 100644
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -69,8 +69,9 @@ struct dmar_pci_notify_info {
extern struct rw_semaphore dmar_global_lock;
extern struct list_head dmar_drhd_units;
-#define for_each_drhd_unit(drhd) \
- list_for_each_entry_rcu(drhd, &dmar_drhd_units, list)
+#define for_each_drhd_unit(drhd) \
+ list_for_each_entry_rcu(drhd, &dmar_drhd_units, list, \
+ dmar_rcu_check())
#define for_each_active_drhd_unit(drhd) \
list_for_each_entry_rcu(drhd, &dmar_drhd_units, list) \
@@ -81,7 +82,8 @@ extern struct list_head dmar_drhd_units;
if (i=drhd->iommu, drhd->ignored) {} else
#define for_each_iommu(i, drhd) \
- list_for_each_entry_rcu(drhd, &dmar_drhd_units, list) \
+ list_for_each_entry_rcu(drhd, &dmar_drhd_units, list, \
+ dmar_rcu_check()) \
if (i=drhd->iommu, 0) {} else
static inline bool dmar_rcu_check(void)
--
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