FAILED: patch "[PATCH] iommu/vt-d: Check identity map for hot-added devices" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 117266fd59ddf46e98e36df09326d861738c6180 Mon Sep 17 00:00:00 2001
From: Lu Baolu <[email protected]>
Date: Mon, 25 Feb 2019 10:46:36 +0800
Subject: [PATCH] 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.

index 00f46021d690..c30b73d41bf2 100644
@@ -4567,16 +4567,19 @@ 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;
 }