Re: [PATCH net] mlxsw: Initialize register query payloads

[Björn Töpel]

Til Kaiser <mail@xxxxxxxx> writes:

> MFGD register queries can exhaust EMAD retries and leave Mellanox
> Spectrum switches stuck during boot or shutdown when running OpenWrt
> built with GCC 15.
>
> An example failure is shown below with the second line wrapped:
>
>   EMAD retries (5/5) (tid=9b544fc100001f35)
>   EMAD reg access failed (tid=9b544fc100001f35,reg_id=90f0(mfgd),
>                           type=query,status=0(operation performed))
>
> On an SN2100, the failure occurs during driver teardown on reboot.
> On an SN3420, it occurs while probing mlxsw_spectrum during boot.
>
> The register query API transmits the supplied payload to the device
> before replacing it with the response. Both MFGD callers pass an
> uninitialized stack buffer, so the request contains arbitrary register
> field values and reserved bits. This makes the request depend on stack
> contents and compiler code generation.
>
> Initialize both MFGD query buffers in the firmware fatal event
> configuration and reporter test paths. The initialization has been
> confirmed to eliminate the boot and shutdown hangs on both switches.
> The subsequent read-modify-write still preserves the other fields
> returned by the device.
>
> Also initialize the FORE fan fault query and the MOGCR mirroring policer
> base query, which pass entirely uninitialized payloads. Restore the MTMP
> query initialization in the temperature history reset path, where only
> the slot and sensor index fields are set before querying the register.
>
> This follows commit 5b0907407e7f ("mlxsw: core: Zero payload buffers for
> couple of registers"), which initialized other query payloads after a
> firmware field length bug caused firmware to consume uninitialized data.

Hmm, isn't this pointing to that the query should be more robust,
instead of relying on zeroing receive buffers pre-call? Maybe just fixup
query instead?


Björn