[PATCH] Skip vfio in the scenario of non-privileged mode

[PATCH] Skip vfio in the scenario of non-privileged mode

[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.

Signed-off-by: Yang Ming <ming.1.yang@nokia-sbell.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 7132e24cba..1679d29263 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>
@@ -1083,6 +1084,7 @@ 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();
 
@@ -1119,6 +1121,15 @@ rte_vfio_enable(const char *modname)
 		return 0;
 	}
 
+	/* return 0 if VFIO directory not exist for container with non-privileged mode */
+	dir = opendir(VFIO_DIR);
+	if (dir == NULL) {
+		EAL_LOG(DEBUG,
+			"VFIO directory 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;
-- 
2.34.1

Re: [PATCH] Skip vfio in the scenario of non-privileged mode

[Stephen Hemminger]

On Fri, 17 Jan 2025 15:28:47 +0800
Yang Ming <ming.1.yang@nokia-sbell.com> wrote:

> 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.
> 
> Signed-off-by: Yang Ming <ming.1.yang@nokia-sbell.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 7132e24cba..1679d29263 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>
> @@ -1083,6 +1084,7 @@ 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();
>  
> @@ -1119,6 +1121,15 @@ rte_vfio_enable(const char *modname)
>  		return 0;
>  	}
>  
> +	/* return 0 if VFIO directory not exist for container with non-privileged mode */
> +	dir = opendir(VFIO_DIR);
> +	if (dir == NULL) {
> +		EAL_LOG(DEBUG,
> +			"VFIO directory not exist, skipping VFIO support...");
> +		return 0;
> +	}
> +	closedir(dir);

You need to test the non-container cases.
If vfio is loaded /dev/vfio is a character device (not a directory)

Also looks suspicious that VFIO_DIR is defined but never used currently.