From: David Woodhouse <dwmw@amazon.co.uk>
Date: Tue, 6 Oct 2020 11:09:19 +0000 (+0100)
Subject: genirq: Ensure affinity masks include one present CPU for each vector
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=50052ed99db8e1ad9b29a5ec79d901b08deef435;p=users%2Fdwmw2%2Flinux.git

genirq: Ensure affinity masks include one present CPU for each vector

Where allocating more MSI-X vectors for a device than there are CPUs in
the system, irq_build_affinity_masks() will end up creating affinities
for some vectors which don't include *any* present CPUs.

Make it try harder to assign at least one present CPU to each vector.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---

diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
index 3fba9220fea65..a53c4e6f04345 100644
--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -364,12 +364,17 @@ static int irq_build_affinity_masks(unsigned int startvec, unsigned int numvecs,
 		cpumask_copy(npresmsk, cpu_present_mask);
 
 	/* Spread on present CPUs starting from affd->pre_vectors */
-	ret = __irq_build_affinity_masks(curvec, numvecs, firstvec,
-					 node_to_cpumask, cpu_present_mask,
-					 nmsk, masks);
-	if (ret < 0)
-		goto fail_build_affinity;
-	nr_present = ret;
+	while (nr_present < numvecs) {
+		curvec = firstvec + nr_present;
+		ret = __irq_build_affinity_masks(curvec, numvecs, firstvec,
+						 node_to_cpumask, npresmsk,
+						 nmsk, masks);
+		if (ret < 0)
+			goto fail_build_affinity;
+		if (!ret)
+			break;
+		nr_present += ret;
+	}
 
 	/*
 	 * Spread on non present CPUs starting from the next vector to be