Patch "iommu/vt-d: Fix IOMMU lookup for SR-IOV Virtual Functions" has been added to the 4.8-stable tree

This is a note to let you know that I've just added the patch titled

iommu/vt-d: Fix IOMMU lookup for SR-IOV Virtual Functions

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
iommu-vt-d-fix-iommu-lookup-for-sr-iov-virtual-functions.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Ashok Raj <[email protected]>
Date: Fri, 21 Oct 2016 15:32:05 -0700
Subject: iommu/vt-d: Fix IOMMU lookup for SR-IOV Virtual Functions
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From: Ashok Raj <[email protected]>

commit 1c387188c60f53b338c20eee32db055dfe022a9b upstream.

The VT-d specification (§8.3.3) says:
‘Virtual Functions’ of a ‘Physical Function’ are under the scope of the same remapping unit as the ‘Physical Function’.

The BIOS is not required to list all the possible VFs in the scope tables, and arguably *shouldn't* make any attempt to do so, since there could be a huge number of them.

This has been broken basically for ever — the VF is never going to match against a specific unit's scope, so it ends up being assigned to the INCLUDE_ALL IOMMU. Which was always actually correct by coincidence, but now we're looking at Root-Complex integrated devices with SR-IOV support it's going to start being wrong.

Fix it to simply use pci_physfn() before doing the lookup for PCI devices.

---
 drivers/iommu/dmar.c        |    4 +++-
 drivers/iommu/intel-iommu.c |   13 +++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

@@ -338,7 +338,9 @@ static int dmar_pci_bus_notifier(struct
 	struct pci_dev *pdev = to_pci_dev(data);
 	struct dmar_pci_notify_info *info;
 
-	/* Only care about add/remove events for physical functions */
+	/* Only care about add/remove events for physical functions.
+	 * For VFs we actually do the lookup based on the corresponding
+	 * PF in device_to_iommu() anyway. */
 	if (pdev->is_virtfn)
 		return NOTIFY_DONE;
 	if (action != BUS_NOTIFY_ADD_DEVICE &&

@@ -892,7 +892,13 @@ static struct intel_iommu *device_to_iom
 		return NULL;
 
 	if (dev_is_pci(dev)) {
+		struct pci_dev *pf_pdev;
+
 		pdev = to_pci_dev(dev);
+		/* VFs aren't listed in scope tables; we need to look up
+		 * the PF instead to find the IOMMU. */
+		pf_pdev = pci_physfn(pdev);
+		dev = &pf_pdev->dev;
 		segment = pci_domain_nr(pdev->bus);
 	} else if (has_acpi_companion(dev))
 		dev = &ACPI_COMPANION(dev)->dev;

@@ -905,6 +911,13 @@ static struct intel_iommu *device_to_iom
 		for_each_active_dev_scope(drhd->devices,
 					  drhd->devices_cnt, i, tmp) {
 			if (tmp == dev) {
+				/* For a VF use its original BDF# not that of the PF
+				 * which we used for the IOMMU lookup. Strictly speaking
+				 * we could do this for all PCI devices; we only need to
+				 * get the BDF# from the scope table for ACPI matches. */
+				if (pdev->is_virtfn)
+					goto got_pdev;
+
 				*bus = drhd->devices[i].bus;
 				*devfn = drhd->devices[i].devfn;
 				goto out;

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/iommu-vt-d-fix-iommu-lookup-for-sr-iov-virtual-functions.patch