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

[Stephen Hemminger <stephen@networkplumber.org>]

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.