Patch "iommu/vt-d: Fix pasid table size encoding" has been added to the 4.4-stable tree

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

iommu/vt-d: Fix pasid table size encoding

to the 4.4-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-pasid-table-size-encoding.patch
and it can be found in the queue-4.4 subdirectory.

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

From: Jacob Pan <[email protected]>
Date: Tue, 6 Dec 2016 10:14:23 -0800
Subject: iommu/vt-d: Fix pasid table size encoding

From: Jacob Pan <[email protected]>

commit 65ca7f5f7d1cdde6c25172fe6107cd16902f826f upstream.

Different encodings are used to represent supported PASID bits and number of PASID table entries.
The current code assigns ecap_pss directly to extended context table entry PTS which is wrong and could result in writing non-zero bits to the reserved fields. IOMMU fault reason 11 will be reported when reserved bits are nonzero. This patch converts ecap_pss to extend context entry pts encoding based on VT-d spec. Chapter 9.4 as follows:
- number of PASID bits = ecap_pss + 1
- number of PASID table entries = 2^(pts + 5)
Software assigned limit of pasid_max value is also respected to match the allocation limitation of PASID table.

---
 drivers/iommu/intel-iommu.c |   23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

@@ -5020,6 +5020,25 @@ static void intel_iommu_remove_device(st
 }
 
 #ifdef CONFIG_INTEL_IOMMU_SVM
+#define MAX_NR_PASID_BITS (20)
+static inline unsigned long intel_iommu_get_pts(struct intel_iommu *iommu)
+{
+	/*
+	 * Convert ecap_pss to extend context entry pts encoding, also
+	 * respect the soft pasid_max value set by the iommu.
+	 * - number of PASID bits = ecap_pss + 1
+	 * - number of PASID table entries = 2^(pts + 5)
+	 * Therefore, pts = ecap_pss - 4
+	 * e.g. KBL ecap_pss = 0x13, PASID has 20 bits, pts = 15
+	 */
+	if (ecap_pss(iommu->ecap) < 5)
+		return 0;
+
+	/* pasid_max is encoded as actual number of entries not the bits */
+	return find_first_bit((unsigned long *)&iommu->pasid_max,
+			MAX_NR_PASID_BITS) - 5;
+}
+
 int intel_iommu_enable_pasid(struct intel_iommu *iommu, struct intel_svm_dev *sdev)
 {
 	struct device_domain_info *info;

@@ -5052,7 +5071,9 @@ int intel_iommu_enable_pasid(struct inte
 
 	if (!(ctx_lo & CONTEXT_PASIDE)) {
 		context[1].hi = (u64)virt_to_phys(iommu->pasid_state_table);
-		context[1].lo = (u64)virt_to_phys(iommu->pasid_table) | ecap_pss(iommu->ecap);
+		context[1].lo = (u64)virt_to_phys(iommu->pasid_table) |
+			intel_iommu_get_pts(iommu);
+
 		wmb();
 		/* CONTEXT_TT_MULTI_LEVEL and CONTEXT_TT_DEV_IOTLB are both
 		 * extended to permit requests-with-PASID if the PASIDE bit

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

queue-4.4/iommu-vt-d-fix-pasid-table-size-encoding.patch