Re: [PATCH i-g-t] lib/igt_sriov_device: Update igt_sriov_enable_vfs helper

[Jani Nikula <jani.nikula@intel.com>]

On Mon, 20 Apr 2026, Jakub Kolakowski <jakub1.kolakowski@intel.com> wrote:
> Some platforms may expose sriov capability and sriov_totalvfs will be
> greater than 0 while the driver actually doesn't support the platform.
> In such case igt_sriov_is_pf() helper that checks for sriov_totalvfs
> will pass.
> Add additional check within igt_sriov_enable_vfs() function to check if
> writing to sriov_numvfs was successfull and what errno was returned
> during this operation. ENOENT will mean that SR-IOV isn't supported for
> given configuration. In such case test will skip instead of failing.
>
> Cc: Adam Miszczak <adam.miszczak@linux.intel.com>
> Cc: Lukasz Laguna <lukasz.laguna@intel.com>
> Cc: Marcin Bernatowicz <marcin.bernatowicz@linux.intel.com>
> Cc: Katarzyna Piecielska <katarzyna.piecielska@intel.com>
> Signed-off-by: Jakub Kolakowski <jakub1.kolakowski@intel.com>
> ---
>  lib/igt_sriov_device.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/lib/igt_sriov_device.c b/lib/igt_sriov_device.c
> index 1f4c3ac04..3fadcf0aa 100644
> --- a/lib/igt_sriov_device.c
> +++ b/lib/igt_sriov_device.c
> @@ -174,10 +174,16 @@ unsigned int igt_sriov_get_enabled_vfs(int pf)
>   */
>  void igt_sriov_enable_vfs(int pf, unsigned int num_vfs)
>  {
> +	bool ret;
> +
>  	igt_assert(num_vfs > 0);
>  
>  	igt_debug("Enabling %u VFs\n", num_vfs);
> -	pf_attr_set_u32(pf, "device/sriov_numvfs", num_vfs);
> +	ret = __pf_attr_set_u32(pf, "device/sriov_numvfs", num_vfs);
> +
> +	igt_require_f(!(ret == false && errno == ENOENT), "SR-IOV not supported\n");

You can only trust errno immediately after the failing libc function.

There are so many things happening in __pf_attr_set_u32() and the IGT
functions it calls that this is completely unreliable.

The way the igt_sysfs_set_u32() stuff are written, you need to make them
propagate an int -errno return value from deep down to check for ENOENT.

Or check for SR-IOV separately some other way.

BR,
Jani.


> +
> +	igt_assert_f(ret, "Failed to write %u to device/sriov_numvfs (%s)\n", num_vfs, strerror(errno));
>  }
>  
>  /**

-- 
Jani Nikula, Intel