Introduce utility functions to print IRQ affinity settings (smp_affinity
and effective_affinity) via the proc filesystem.

Specifically, add:
- print_proc_irq_smp_affinity() and print_proc_irq_effective_affinity()
  to print the current affinity states.

These helpers will be used in subsequent patches to print affinity
settings for debugging in the KVM IRQ test when timeouts occur.

Signed-off-by: Josh Hilke <jrhilke@google.com>
---
 .../testing/selftests/kvm/include/proc_util.h |  4 +++
 tools/testing/selftests/kvm/lib/proc_util.c   | 30 +++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/proc_util.h b/tools/testing/selftests/kvm/include/proc_util.h
index e381c7818275..e0e8f29c570c 100644
--- a/tools/testing/selftests/kvm/include/proc_util.h
+++ b/tools/testing/selftests/kvm/include/proc_util.h
@@ -8,4 +8,8 @@ unsigned int vfio_msix_to_host_irq(const char *vfio_device_bdf, int msix);
 
 FILE *open_proc_irq_smp_affinity_list(unsigned int irq);
 void write_proc_irq_smp_affinity_list(FILE *fp, unsigned int irq, int irq_cpu);
+
+void print_proc_irq_smp_affinity(unsigned int irq);
+void print_proc_irq_effective_affinity(unsigned int irq);
+
 #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 938c90d94f4d..24a8de92e229 100644
--- a/tools/testing/selftests/kvm/lib/proc_util.c
+++ b/tools/testing/selftests/kvm/lib/proc_util.c
@@ -58,3 +58,33 @@ void write_proc_irq_smp_affinity_list(FILE *fp, unsigned int irq, int irq_cpu)
 	TEST_ASSERT(ret > 0, "Failed to affinitize IRQ-%u to CPU %d", irq, irq_cpu);
 	fflush(fp);
 }
+
+static void print_proc_irq_file(unsigned int irq, const char *file)
+{
+	char path[PATH_MAX];
+	char buf[256];
+	FILE *fp;
+
+	snprintf(path, sizeof(path), "/proc/irq/%u/%s", irq, file);
+	fp = fopen(path, "r");
+	if (!fp) {
+		printf("  Failed to open %s\n", path);
+		return;
+	}
+
+	if (fgets(buf, sizeof(buf), fp)) {
+		buf[strcspn(buf, "\n")] = 0;
+		printf("  %s: %s\n", path, buf);
+	}
+	fclose(fp);
+}
+
+void print_proc_irq_smp_affinity(unsigned int irq)
+{
+	print_proc_irq_file(irq, "smp_affinity");
+}
+
+void print_proc_irq_effective_affinity(unsigned int irq)
+{
+	print_proc_irq_file(irq, "effective_affinity");
+}
-- 
2.54.0.1032.g2f8565e1d1-goog