[PATCH v4] eal/linux: skip vfio for non-privileged container

[Yang Ming]

DPDK detect vfio container according the existence of vfio
module. But for container with non-privileged mode, there is
possibility that no VFIO_DIR(/dev/vfio) mapping from host to
container when host have both Intel NIC and Mellanox NIC but
this conntainer only allocate VFs from Mellanox NIC.
In this case, vfio kernel module has already been loaded from
the host.
This scenario will cause the error log occurs in DPDK primary
process as below:
'EAL:   cannot open VFIO container, error 2 (No such file or
directory)'
'EAL: VFIO support could not be initialized'
Because `rte_vfio_enable()` call `rte_vfio_get_container_fd()`
to execute `vfio_container_fd = open(VFIO_CONTAINER_PATH,
O_RDWR);` but VFIO_CONTAINER_PATH(/dev/vfio/vfio) doesn't exist
in this container.
This scenario will also lead to the delay of DPDK secondary
process because `default_vfio_cfg->vfio_enabled = 0` and
`default_vfio_cfg->vfio_container_fd = -1`, socket error will
be set in DPDK primary process when it sync this info to
the secondary process.
This patch use to skip this kind of useless detection for this
scenario.

Acked-by: Anatoly Burakov <anatoly.burakov at intel.com>

Signed-off-by: Yang Ming <mosesyyoung at gmail.com>
---
 lib/eal/linux/eal_vfio.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/lib/eal/linux/eal_vfio.c b/lib/eal/linux/eal_vfio.c
index 2f5f221a0d..805f0ff92c 100644
--- a/lib/eal/linux/eal_vfio.c
+++ b/lib/eal/linux/eal_vfio.c
@@ -7,6 +7,7 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <sys/ioctl.h>
+#include <dirent.h>
 
 #include <rte_errno.h>
 #include <rte_log.h>
@@ -1089,6 +1090,7 @@ rte_vfio_enable(const char *modname)
 	/* initialize group list */
 	int i, j;
 	int vfio_available;
+	DIR *dir;
 	const struct internal_config *internal_conf =
 		eal_get_internal_configuration();
 
@@ -1125,6 +1127,15 @@ rte_vfio_enable(const char *modname)
 		return 0;
 	}
 
+	/* VFIO directory might not exist (e.g., unprivileged containers) */
+	dir = opendir(VFIO_DIR);
+	if (dir == NULL) {
+		EAL_LOG(DEBUG,
+			"VFIO directory does not exist, skipping VFIO support...");
+		return 0;
+	}
+	closedir(dir);
+
 	if (internal_conf->process_type == RTE_PROC_PRIMARY) {
 		if (vfio_mp_sync_setup() == -1) {
 			default_vfio_cfg->vfio_container_fd = -1;
-- 
2.49.0.windows.1