linux-kernel - [PATCH] iommu/vt-d: Fix PCI bus rescan device hot add

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Date:   Thu, 13 Jan 2022 05:23:18 -0800
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        "Lu Baolu" <baolu.lu@...ux.intel.com>
Cc:     Jacob Pan <jacob.jun.pan@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        "Kumar, Sanjay K" <sanjay.k.kumar@...el.com>
Subject: [PATCH] iommu/vt-d: Fix PCI bus rescan device hot add

During PCI bus rescan, adding new devices involve two notifiers.
1. dmar_pci_bus_notifier()
2. iommu_bus_notifier()
The current code sets #1 as low priority (INT_MIN) which resulted in #2
being invoked first. The result is that struct device pointer cannot be
found in DRHD search for the new device's DMAR/IOMMU. Subsequently, the
device is put under the "catch-all" IOMMU instead of the correct one.

This could cause system hang when device TLB invalidation is sent to the
wrong IOMMU. Invalidation timeout error or hard lockup can be observed.

This patch fixes the issue by setting a higher priority for
dmar_pci_bus_notifier. DRHD search for a new device will find the
correct IOMMU.

Fixes: 59ce0515cdaf ("iommu/vt-d: Update DRHD/RMRR/ATSR device scope")
Reported-by: Zhang, Bernice <bernice.zhang@...el.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
---
 drivers/iommu/intel/dmar.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index 915bff76fe96..5d07e5b89c2e 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -385,7 +385,7 @@ static int dmar_pci_bus_notifier(struct notifier_block *nb,

 static struct notifier_block dmar_pci_bus_nb = {
 	.notifier_call = dmar_pci_bus_notifier,
-	.priority = INT_MIN,
+	.priority = INT_MAX,
 };

 static struct dmar_drhd_unit *
-- 
2.25.1