[PATCH 15/33] vfio: selftests: Enable asserting MSI eventfds not firing

[David Matlack <dmatlack@google.com>]

Make it possible to assert that a given MSI eventfd did _not_ fire by
adding a helper to mark an eventfd non-blocking. Demonstrate this in
vfio_pci_device_test by asserting the MSI eventfd did not fire before
vfio_pci_irq_trigger().

Signed-off-by: David Matlack <dmatlack@google.com>
---
 tools/testing/selftests/vfio/lib/include/vfio_util.h | 12 ++++++++++++
 tools/testing/selftests/vfio/vfio_pci_device_test.c  | 10 +++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/vfio/lib/include/vfio_util.h b/tools/testing/selftests/vfio/lib/include/vfio_util.h
index db08646c2819..9c928fcc00e2 100644
--- a/tools/testing/selftests/vfio/lib/include/vfio_util.h
+++ b/tools/testing/selftests/vfio/lib/include/vfio_util.h
@@ -2,6 +2,7 @@
 #ifndef SELFTESTS_VFIO_LIB_INCLUDE_VFIO_UTIL_H
 #define SELFTESTS_VFIO_LIB_INCLUDE_VFIO_UTIL_H
 
+#include <fcntl.h>
 #include <string.h>
 #include <linux/vfio.h>
 #include <linux/list.h>
@@ -130,6 +131,17 @@ void vfio_pci_irq_enable(struct vfio_pci_device *device, u32 index,
 void vfio_pci_irq_disable(struct vfio_pci_device *device, u32 index);
 void vfio_pci_irq_trigger(struct vfio_pci_device *device, u32 index, u32 vector);
 
+static inline void fcntl_set_nonblock(int fd)
+{
+	int r;
+
+	r = fcntl(fd, F_GETFL, 0);
+	VFIO_ASSERT_NE(r, -1, "F_GETFL failed for fd %d\n", fd);
+
+	r = fcntl(fd, F_SETFL, r | O_NONBLOCK);
+	VFIO_ASSERT_NE(r, -1, "F_SETFL O_NONBLOCK failed for fd %d\n", fd);
+}
+
 static inline void vfio_pci_msi_enable(struct vfio_pci_device *device,
 				       u32 vector, int count)
 {
diff --git a/tools/testing/selftests/vfio/vfio_pci_device_test.c b/tools/testing/selftests/vfio/vfio_pci_device_test.c
index 82e3c947f45d..1b5c2ff77e3f 100644
--- a/tools/testing/selftests/vfio/vfio_pci_device_test.c
+++ b/tools/testing/selftests/vfio/vfio_pci_device_test.c
@@ -129,6 +129,7 @@ FIXTURE_TEARDOWN(vfio_pci_irq_test)
 TEST_F(vfio_pci_irq_test, enable_trigger_disable)
 {
 	bool msix = variant->irq_index == VFIO_PCI_MSIX_IRQ_INDEX;
+	int msi_eventfd;
 	u32 count;
 	u64 value;
 	int i;
@@ -147,8 +148,15 @@ TEST_F(vfio_pci_irq_test, enable_trigger_disable)
 	printf("MSI%s: enabled %d interrupts\n", msix ? "-x" : "", count);
 
 	for (i = 0; i < count; i++) {
+		msi_eventfd = self->device->msi_eventfds[i];
+
+		fcntl_set_nonblock(msi_eventfd);
+		ASSERT_EQ(-1, read(msi_eventfd, &value, 8));
+		ASSERT_EQ(EAGAIN, errno);
+
 		vfio_pci_irq_trigger(self->device, variant->irq_index, i);
-		ASSERT_EQ(8, read(self->device->msi_eventfds[i], &value, 8));
+
+		ASSERT_EQ(8, read(msi_eventfd, &value, 8));
 		ASSERT_EQ(1, value);
 	}
 
-- 
2.50.0.rc2.701.gf1e915cc24-goog