[PATCH v8 5/6] vfio: selftests: Retry on EAGAIN during device reset

[Josh Hilke <jrhilke@google.com>]

Add retry logic to vfio_pci_device_reset() to handle the case where PCI
resets fail due to lock contention, in which case
pci_try_reset_function() returns -EAGAIN.

Suggested-by: David Matlack <dmatlack@google.com>
Signed-off-by: Josh Hilke <jrhilke@google.com>
---
 .../vfio/lib/include/libvfio/vfio_pci_device.h       |  1 +
 tools/testing/selftests/vfio/lib/vfio_pci_device.c   | 20 +++++++++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h b/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
index 89a039ab3075..e19bd94b8dd2 100644
--- a/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
+++ b/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
@@ -43,6 +43,7 @@ void vfio_pci_device_free(struct vfio_pci_device *device);
 struct vfio_pci_device *vfio_pci_device_init(const char *bdf, struct iommu *iommu);
 void vfio_pci_device_cleanup(struct vfio_pci_device *device);
 
+int __vfio_pci_device_reset(struct vfio_pci_device *device);
 void vfio_pci_device_reset(struct vfio_pci_device *device);
 
 void vfio_pci_config_access(struct vfio_pci_device *device, bool write,
diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_device.c b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
index 65a4fffb480c..4063a0e2b3df 100644
--- a/tools/testing/selftests/vfio/lib/vfio_pci_device.c
+++ b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include <dirent.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <libgen.h>
 #include <stdint.h>
@@ -259,9 +260,26 @@ void vfio_pci_config_access(struct vfio_pci_device *device, bool write,
 		       write ? "write to" : "read from", config);
 }
 
+int __vfio_pci_device_reset(struct vfio_pci_device *device)
+{
+	if (ioctl(device->fd, VFIO_DEVICE_RESET, NULL))
+		return -errno;
+
+	return 0;
+}
+
 void vfio_pci_device_reset(struct vfio_pci_device *device)
 {
-	ioctl_assert(device->fd, VFIO_DEVICE_RESET, NULL);
+	int retries = 20;
+	int r;
+
+	do {
+		r = __vfio_pci_device_reset(device);
+		if (r == -EAGAIN)
+			usleep(10000);
+	} while (r == -EAGAIN && retries-- > 0);
+
+	VFIO_ASSERT_EQ(r, 0, "ioctl(device->fd, VFIO_DEVICE_RESET) failed\n");
 }
 
 void vfio_pci_group_setup(struct vfio_pci_device *device, const char *bdf)

-- 
2.55.0.508.g3f0d502094-goog