linux-kernel - [PATCH 1/1] iommu/vt-d: Check identity map for hot-added devices

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Date:   Mon, 25 Feb 2019 10:46:36 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     joro@...tes.org, dwmw2@...radead.org
Cc:     ashok.raj@...el.com, jacob.jun.pan@...ux.intel.com,
        jisben@...gle.com, xmdong@...gle.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>, stable@...r.kernel.org
Subject: [PATCH 1/1] iommu/vt-d: Check identity map for hot-added devices

The Intel IOMMU driver will put devices into a static identity
mapped domain during boot if the kernel parameter "iommu=pt" is
used. That means the IOMMU hardware will translate a DMA address
into the same memory address.

Unfortunately, hot-added devices are not subject to this. That
results in some devices not working properly after hot added. A
quick way to reproduce this issue is to boot a system with

    iommu=pt

and, remove then readd the pci device with

    echo 1 > /sys/bus/pci/devices/[pci_source_id]/remove
    echo 1 > /sys/bus/pci/rescan

You will find the identity mapped domain was replaced with a
normal domain.

Cc: Ashok Raj <ashok.raj@...el.com>
Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: stable@...r.kernel.org
Reported-by: Jis Ben <jisben@...gle.com>
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Tested-by: James Dong <xmdong@...gle.com>
---
 drivers/iommu/intel-iommu.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index af23cfc2a05e..4f77657a9c25 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4564,16 +4564,19 @@ static int device_notifier(struct notifier_block *nb,
 	if (iommu_dummy(dev))
 		return 0;
 
-	if (action != BUS_NOTIFY_REMOVED_DEVICE)
-		return 0;
-
-	domain = find_domain(dev);
-	if (!domain)
-		return 0;
+	if (action == BUS_NOTIFY_REMOVED_DEVICE) {
+		domain = find_domain(dev);
+		if (!domain)
+			return 0;
 
-	dmar_remove_one_dev_info(dev);
-	if (!domain_type_is_vm_or_si(domain) && list_empty(&domain->devices))
-		domain_exit(domain);
+		dmar_remove_one_dev_info(dev);
+		if (!domain_type_is_vm_or_si(domain) &&
+		    list_empty(&domain->devices))
+			domain_exit(domain);
+	} else if (action == BUS_NOTIFY_ADD_DEVICE) {
+		if (iommu_should_identity_map(dev, 1))
+			domain_add_dev_info(si_domain, dev);
+	}
 
 	return 0;
 }
-- 
2.17.1