[RFC PATCH 19/21] vfio: selftests: Initialize vfio_pci_device using a VFIO cdev FD

[Vipin Sharma <vipinsh@google.com>]

Use the given VFIO cdev FD to initialize vfio_pci_device in VFIO
selftests. Add the assertion to make sure that passed cdev FD is not
used with legacy VFIO APIs. If VFIO cdev FD is provided then do not open
the device instead use the FD for any interaction with the device.

This API will allow to write selftests where VFIO device FD is preserved
using liveupdate and retrieved later using liveupdate ioctl after kexec.

Signed-off-by: Vipin Sharma <vipinsh@google.com>
---
 .../selftests/vfio/lib/include/vfio_util.h    |  1 +
 .../selftests/vfio/lib/vfio_pci_device.c      | 33 +++++++++++++++----
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/vfio/lib/include/vfio_util.h b/tools/testing/selftests/vfio/lib/include/vfio_util.h
index ed31606e01b7..8ec60a62a0d1 100644
--- a/tools/testing/selftests/vfio/lib/include/vfio_util.h
+++ b/tools/testing/selftests/vfio/lib/include/vfio_util.h
@@ -203,6 +203,7 @@ const char *vfio_pci_get_cdev_path(const char *bdf);
 extern const char *default_iommu_mode;
 
 struct vfio_pci_device *vfio_pci_device_init(const char *bdf, const char *iommu_mode);
+struct vfio_pci_device *vfio_pci_device_init_fd(int vfio_cdev_fd);
 void vfio_pci_device_cleanup(struct vfio_pci_device *device);
 void vfio_pci_device_reset(struct vfio_pci_device *device);
 
diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_device.c b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
index 0921b2451ba5..cab9c74d2de8 100644
--- a/tools/testing/selftests/vfio/lib/vfio_pci_device.c
+++ b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
@@ -486,13 +486,18 @@ static void vfio_device_attach_iommufd_pt(int device_fd, u32 pt_id)
 	ioctl_assert(device_fd, VFIO_DEVICE_ATTACH_IOMMUFD_PT, &args);
 }
 
-static void vfio_pci_iommufd_setup(struct vfio_pci_device *device, const char *bdf)
+static void vfio_pci_iommufd_setup(struct vfio_pci_device *device,
+				   const char *bdf, int vfio_cdev_fd)
 {
-	const char *cdev_path = vfio_pci_get_cdev_path(bdf);
 
-	device->fd = open(cdev_path, O_RDWR);
+	if (vfio_cdev_fd > 0) {
+		device->fd = vfio_cdev_fd;
+	} else {
+		const char *cdev_path = vfio_pci_get_cdev_path(bdf);
+		device->fd = open(cdev_path, O_RDWR);
+		free((void *)cdev_path);
+	}
 	VFIO_ASSERT_GE(device->fd, 0);
-	free((void *)cdev_path);
 
 	/*
 	 * Require device->iommufd to be >0 so that a simple non-0 check can be
@@ -507,7 +512,9 @@ static void vfio_pci_iommufd_setup(struct vfio_pci_device *device, const char *b
 	vfio_device_attach_iommufd_pt(device->fd, device->ioas_id);
 }
 
-struct vfio_pci_device *vfio_pci_device_init(const char *bdf, const char *iommu_mode)
+struct vfio_pci_device *__vfio_pci_device_init(const char *bdf,
+					       const char *iommu_mode,
+					       int vfio_cdev_fd)
 {
 	struct vfio_pci_device *device;
 
@@ -518,10 +525,13 @@ struct vfio_pci_device *vfio_pci_device_init(const char *bdf, const char *iommu_
 
 	device->iommu_mode = lookup_iommu_mode(iommu_mode);
 
+	VFIO_ASSERT_FALSE(device->iommu_mode->container_path != NULL && vfio_cdev_fd > 0,
+			  "Provide either container path or VFIO cdev FD, not both.\n");
+
 	if (device->iommu_mode->container_path)
 		vfio_pci_container_setup(device, bdf);
 	else
-		vfio_pci_iommufd_setup(device, bdf);
+		vfio_pci_iommufd_setup(device, bdf, vfio_cdev_fd);
 
 	vfio_pci_device_setup(device);
 	vfio_pci_driver_probe(device);
@@ -529,6 +539,17 @@ struct vfio_pci_device *vfio_pci_device_init(const char *bdf, const char *iommu_
 	return device;
 }
 
+struct vfio_pci_device *vfio_pci_device_init(const char *bdf,
+					     const char *iommu_mode)
+{
+	return __vfio_pci_device_init(bdf, iommu_mode, -1);
+}
+
+struct vfio_pci_device *vfio_pci_device_init_fd(int vfio_cdev_fd)
+{
+	return __vfio_pci_device_init(NULL, "iommufd", vfio_cdev_fd);
+}
+
 void vfio_pci_device_cleanup(struct vfio_pci_device *device)
 {
 	int i;
-- 
2.51.0.858.gf9c4a03a3a-goog