[dpdk-dev] [Bug 370] Cannot hotplug VFIO devices if VFIO driver was not loaded at init

[bugzilla@dpdk.org]

https://bugs.dpdk.org/show_bug.cgi?id=370

            Bug ID: 370
           Summary: Cannot hotplug VFIO devices if VFIO driver was not
                    loaded at init
           Product: DPDK
           Version: unspecified
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: core
          Assignee: dev@dpdk.org
          Reporter: anatoly.burakov@intel.com
  Target Milestone: ---

Currently, VFIO device initialization depends upon checking if VFIO is enabled.
That code looks like this:

> int
> rte_vfio_is_enabled(const char *modname)
> {
>     const int mod_available = rte_eal_check_module(modname) > 0;
>     return default_vfio_cfg->vfio_enabled && mod_available;
> }

The `default_vfio_cfg->vfio_enabled` is set at initialization time with
`rte_vfio_enable` function, and is never rechecked afterwards. This makes it so
that if `vfio` driver was not loaded at EAL initialization time, any subsequent
VFIO device initialization will fail.

To fix that, we would have to re-check the existence of a `vfio` driver every
time, however the current API gets in the way, because even though it stores
global state, it is implemented in a way that looks like it is supposed to be
generic and support multiple driver names (and is never used that way - the
only time this API is used is in the EAL initialization when checking for a
specific `vfio` driver - i think it's a safe assumption to make that whatever
implementation of VFIO is in use, it will depend upon the `vfio` kernel
module).

So, current API will need to be changed (it makes no sense anyway) before this
bug can be fixed.

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