[PATCH] PCI/MSI: Ignore affinity if pre/post vector count is more than min_vecs

[Himanshu Madhani <himanshu.madhani@cavium.com>]

From: Michael Hernandez <michael.hernandez@cavium.com>

min_vecs is the minimum amount of vectors needed to operate in MSI-X mode
which may just include the vectors that don't need affinity.

Disabling affinity settings causes the qla2xxx driver scsi_add_host
to fail when blk_mq is enabled as the blk_mq_pci_map_queues expects
affinity masks on each vector.

Fixes: dfef358bd1be ("PCI/MSI: Don't apply affinity if there aren't enough vectors left")
Signed-off-by: Michael Hernandez <michael.hernandez@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Cc: <stable@vger.kernel.org> # 4.10
---
v5 --> v6
o Fixed more review comments from Bjorn. 

v4 --> v5
o Fixed Zero day kernel build failure.

v3 --> v4
o Moved pre/post reserved vector range checks to affinity.c as per
  comments from Bjorn Helgaas.

v2 --> v3
o fixed code as per review comments.

v1 --> v2
o Moved the check from pci_alloc_irq_vectors_affinity() to
  __pci_enable_{msi|msix}_range()

---
 drivers/pci/msi.c         | 14 ++------------
 include/linux/interrupt.h |  4 ++--
 kernel/irq/affinity.c     | 13 ++++++++++++-
 3 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 7f73bacf13ed..a5c13d052f18 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1091,7 +1091,7 @@ static int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
 
 	for (;;) {
 		if (affd) {
-			nvec = irq_calc_affinity_vectors(nvec, affd);
+			nvec = irq_calc_affinity_vectors(minvec, nvec, affd);
 			if (nvec < minvec)
 				return -ENOSPC;
 		}
@@ -1138,7 +1138,7 @@ static int __pci_enable_msix_range(struct pci_dev *dev,
 
 	for (;;) {
 		if (affd) {
-			nvec = irq_calc_affinity_vectors(nvec, affd);
+			nvec = irq_calc_affinity_vectors(minvec, nvec, affd);
 			if (nvec < minvec)
 				return -ENOSPC;
 		}
@@ -1206,16 +1206,6 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
 	if (flags & PCI_IRQ_AFFINITY) {
 		if (!affd)
 			affd = &msi_default_affd;
-
-		if (affd->pre_vectors + affd->post_vectors > min_vecs)
-			return -EINVAL;
-
-		/*
-		 * If there aren't any vectors left after applying the pre/post
-		 * vectors don't bother with assigning affinity.
-		 */
-		if (affd->pre_vectors + affd->post_vectors == min_vecs)
-			affd = NULL;
 	} else {
 		if (WARN_ON(affd))
 			affd = NULL;
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 53144e78a369..63b246dd8258 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -291,7 +291,7 @@ extern int
 irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify);
 
 struct cpumask *irq_create_affinity_masks(int nvec, const struct irq_affinity *affd);
-int irq_calc_affinity_vectors(int maxvec, const struct irq_affinity *affd);
+int irq_calc_affinity_vectors(int minvec, int maxvec, const struct irq_affinity *affd);
 
 #else /* CONFIG_SMP */
 
@@ -331,7 +331,7 @@ irq_create_affinity_masks(int nvec, const struct irq_affinity *affd)
 }
 
 static inline int
-irq_calc_affinity_vectors(int maxvec, const struct irq_affinity *affd)
+irq_calc_affinity_vectors(int minvec, int maxvec, const struct irq_affinity *affd)
 {
 	return maxvec;
 }
diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
index 4544b115f5eb..e70642ed9858 100644
--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -66,6 +66,13 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
 	struct cpumask *masks;
 	cpumask_var_t nmsk;
 
+	/*
+	 * If there aren't any vectors left after applying the pre/post
+	 * vectors don't bother with assigning affinity.
+	 */
+	if (!affv)
+		return NULL;
+
 	if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
 		return NULL;
 
@@ -138,15 +145,19 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
 
 /**
  * irq_calc_affinity_vectors - Calculate the optimal number of vectors
+ * @minvec:	The minimum number of vectors available
  * @maxvec:	The maximum number of vectors available
  * @affd:	Description of the affinity requirements
  */
-int irq_calc_affinity_vectors(int maxvec, const struct irq_affinity *affd)
+int irq_calc_affinity_vectors(int minvec, int maxvec, const struct irq_affinity *affd)
 {
 	int resv = affd->pre_vectors + affd->post_vectors;
 	int vecs = maxvec - resv;
 	int cpus;
 
+	if (resv > minvec)
+		return 0;
+
 	/* Stabilize the cpumasks */
 	get_online_cpus();
 	cpus = cpumask_weight(cpu_online_mask);
-- 
2.12.0.264.gd6db3f2