diff --git a/tools/testing/selftests/kvm/include/proc_util.h b/tools/testing/selftests/kvm/include/proc_util.h
index 704839b6d7af..d1ddc967d11d 100644
--- a/tools/testing/selftests/kvm/include/proc_util.h
+++ b/tools/testing/selftests/kvm/include/proc_util.h
@@ -6,4 +6,6 @@
 
 unsigned int vfio_msix_to_host_irq(const char *vfio_device_bdf, int msix);
 
+void proc_irq_set_smp_affinity(unsigned int irq, int cpu);
+
 #endif /* SELFTEST_KVM_PROC_UTIL_H */
diff --git a/tools/testing/selftests/kvm/lib/proc_util.c b/tools/testing/selftests/kvm/lib/proc_util.c
index 84d30f055a0a..3960b3841d63 100644
--- a/tools/testing/selftests/kvm/lib/proc_util.c
+++ b/tools/testing/selftests/kvm/lib/proc_util.c
@@ -38,3 +38,17 @@ unsigned int vfio_msix_to_host_irq(const char *device_bdf, int msix)
 	return (unsigned int)irq;
 }
 
+void proc_irq_set_smp_affinity(unsigned int irq, int cpu)
+{
+	char path[PATH_MAX];
+	int r, fd;
+
+	snprintf(path, sizeof(path), "/proc/irq/%u/smp_affinity_list", irq);
+	fd = open(path, O_RDWR);
+	TEST_ASSERT(fd >= 0, "Failed to open %s", path);
+
+	r = dprintf(fd, "%d\n", cpu);
+	TEST_ASSERT(r > 0, "Failed to affinitize IRQ-%u to CPU %d", irq, cpu);
+
+	kvm_close(fd);
+}