x86/apic/vector: Fix ordering in vector assignment

Prarit reported that depending on the affinity setting the

' irq $N: Affinity broken due to vector space exhaustion.'

message is showing up in dmesg, but the vector space on the CPUs in the affinity mask is definitely not exhausted.

Shung-Hsi provided traces and analysis which pinpoints the problem:

The ordering of trying to assign an interrupt vector in assign_irq_vector_any_locked() is simply wrong if the interrupt data has a valid node assigned. It does:

1) Try the intersection of affinity mask and node mask
2) Try the node mask
3) Try the full affinity mask
4) Try the full online mask

Obviously #2 and #3 are in the wrong order as the requested affinity mask has to take precedence.

In the observed cases #1 failed because the affinity mask did not contain CPUs from node 0. That made it allocate a vector from node 0, thereby breaking affinity and emitting the misleading message.

Revert the order of #2 and #3 so the full affinity mask without the node intersection is tried before actually affinity is broken.

If no node is assigned then only the full affinity mask and if that fails the full online mask is tried.

Fixes d6ffc6ac83b1 ("x86/vector: Respect affinity mask in irq descriptor")

Reported-by Shung-Hsi Yu <[email protected]>

Reported-by Prarit Bhargava <[email protected]>

Signed-off-by Thomas Gleixner <[email protected]>

Tested-by Shung-Hsi Yu <[email protected]>

Cc [email protected]

---
 arch/x86/kernel/apic/vector.c |   24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

arch/x86/kernel/apic/vector.c +7 -10

@@ -273,20 +273,24 @@ static int assign_irq_vector_any_locked(
 	const struct cpumask *affmsk = irq_data_get_affinity_mask(irqd);
 	int node = irq_data_get_node(irqd);
 
-	if (node == NUMA_NO_NODE)
-		goto all;
-	/* Try the intersection of @affmsk and node mask */
-	cpumask_and(vector_searchmask, cpumask_of_node(node), affmsk);
-	if (!assign_vector_locked(irqd, vector_searchmask))
-		return 0;
-	/* Try the node mask */
-	if (!assign_vector_locked(irqd, cpumask_of_node(node)))
-		return 0;
-all:
+	if (node != NUMA_NO_NODE) {
+		/* Try the intersection of @affmsk and node mask */
+		cpumask_and(vector_searchmask, cpumask_of_node(node), affmsk);
+		if (!assign_vector_locked(irqd, vector_searchmask))
+			return 0;
+	}
+
 	/* Try the full affinity mask */
 	cpumask_and(vector_searchmask, affmsk, cpu_online_mask);
 	if (!assign_vector_locked(irqd, vector_searchmask))
 		return 0;

Prarit reported that depending on the affinity setting the

' irq $N: Affinity broken due to vector space exhaustion.'

message is showing up in dmesg, but the vector space on the CPUs in the affinity mask is definitely not exhausted.

Shung-Hsi provided traces and analysis which pinpoints the problem:

The ordering of trying to assign an interrupt vector in assign_irq_vector_any_locked() is simply wrong if the interrupt data has a valid node assigned. It does:

1) Try the intersection of affinity mask and node mask
2) Try the node mask
3) Try the full affinity mask
4) Try the full online mask

Obviously #2 and #3 are in the wrong order as the requested affinity mask has to take precedence.

In the observed cases #1 failed because the affinity mask did not contain CPUs from node 0. That made it allocate a vector from node 0, thereby breaking affinity and emitting the misleading message.

Revert the order of #2 and #3 so the full affinity mask without the node intersection is tried before actually affinity is broken.

If no node is assigned then only the full affinity mask and if that fails the full online mask is tried.

Fixes d6ffc6ac83b1 ("x86/vector: Respect affinity mask in irq descriptor")

Reported-by Shung-Hsi Yu <[email protected]>

Reported-by Prarit Bhargava <[email protected]>

Signed-off-by Thomas Gleixner <[email protected]>

Tested-by Shung-Hsi Yu <[email protected]>

Cc [email protected]

---
 arch/x86/kernel/apic/vector.c |   24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

arch/x86/kernel/apic/vector.c +7 -10

@@ -273,20 +273,24 @@ static int assign_irq_vector_any_locked(
 	const struct cpumask *affmsk = irq_data_get_affinity_mask(irqd);
 	int node = irq_data_get_node(irqd);
 
-	if (node == NUMA_NO_NODE)
-		goto all;
-	/* Try the intersection of @affmsk and node mask */
-	cpumask_and(vector_searchmask, cpumask_of_node(node), affmsk);
-	if (!assign_vector_locked(irqd, vector_searchmask))
-		return 0;
-	/* Try the node mask */
-	if (!assign_vector_locked(irqd, cpumask_of_node(node)))
-		return 0;
-all:
+	if (node != NUMA_NO_NODE) {
+		/* Try the intersection of @affmsk and node mask */
+		cpumask_and(vector_searchmask, cpumask_of_node(node), affmsk);
+		if (!assign_vector_locked(irqd, vector_searchmask))
+			return 0;
+	}
+
 	/* Try the full affinity mask */
 	cpumask_and(vector_searchmask, affmsk, cpu_online_mask);
 	if (!assign_vector_locked(irqd, vector_searchmask))
 		return 0;

Prarit reported that depending on the affinity setting the

' irq $N: Affinity broken due to vector space exhaustion.'

message is showing up in dmesg, but the vector space on the CPUs in the affinity mask is definitely not exhausted.

Shung-Hsi provided traces and analysis which pinpoints the problem:

The ordering of trying to assign an interrupt vector in assign_irq_vector_any_locked() is simply wrong if the interrupt data has a valid node assigned. It does:

1) Try the intersection of affinity mask and node mask
2) Try the node mask
3) Try the full affinity mask
4) Try the full online mask

Obviously #2 and #3 are in the wrong order as the requested affinity mask has to take precedence.

In the observed cases #1 failed because the affinity mask did not contain CPUs from node 0. That made it allocate a vector from node 0, thereby breaking affinity and emitting the misleading message.

Revert the order of #2 and #3 so the full affinity mask without the node intersection is tried before actually affinity is broken.

If no node is assigned then only the full affinity mask and if that fails the full online mask is tried.

Fixes d6ffc6ac83b1 ("x86/vector: Respect affinity mask in irq descriptor")

Reported-by Shung-Hsi Yu <[email protected]>

Reported-by Prarit Bhargava <[email protected]>

Signed-off-by Thomas Gleixner <[email protected]>

Tested-by Shung-Hsi Yu <[email protected]>

Cc [email protected]