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    Subject[PATCH 5.14 114/151] i40e: fix endless loop under rtnl
    Date
    From: Jiri Benc <jbenc@redhat.com>

    [ Upstream commit 857b6c6f665cca9828396d9743faf37fd09e9ac3 ]

    The loop in i40e_get_capabilities can never end. The problem is that
    although i40e_aq_discover_capabilities returns with an error if there's
    a firmware problem, the returned error is not checked. There is a check for
    pf->hw.aq.asq_last_status but that value is set to I40E_AQ_RC_OK on most
    firmware problems.

    When i40e_aq_discover_capabilities encounters a firmware problem, it will
    encounter the same problem on its next invocation. As the result, the loop
    becomes endless. We hit this with I40E_ERR_ADMIN_QUEUE_TIMEOUT but looking
    at the code, it can happen with a range of other firmware errors.

    I don't know what the correct behavior should be: whether the firmware
    should be retried a few times, or whether pf->hw.aq.asq_last_status should
    be always set to the encountered firmware error (but then it would be
    pointless and can be just replaced by the i40e_aq_discover_capabilities
    return value). However, the current behavior with an endless loop under the
    rtnl mutex(!) is unacceptable and Intel has not submitted a fix, although we
    explained the bug to them 7 months ago.

    This may not be the best possible fix but it's better than hanging the whole
    system on a firmware bug.

    Fixes: 56a62fc86895 ("i40e: init code and hardware support")
    Tested-by: Stefan Assmann <sassmann@redhat.com>
    Signed-off-by: Jiri Benc <jbenc@redhat.com>
    Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
    Tested-by: Dave Switzer <david.switzer@intel.com>
    Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/ethernet/intel/i40e/i40e_main.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
    index 1d1f52756a93..772dd05a0ae8 100644
    --- a/drivers/net/ethernet/intel/i40e/i40e_main.c
    +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
    @@ -10110,7 +10110,7 @@ static int i40e_get_capabilities(struct i40e_pf *pf,
    if (pf->hw.aq.asq_last_status == I40E_AQ_RC_ENOMEM) {
    /* retry with a larger buffer */
    buf_len = data_size;
    - } else if (pf->hw.aq.asq_last_status != I40E_AQ_RC_OK) {
    + } else if (pf->hw.aq.asq_last_status != I40E_AQ_RC_OK || err) {
    dev_info(&pf->pdev->dev,
    "capability discovery failed, err %s aq_err %s\n",
    i40e_stat_str(&pf->hw, err),
    --
    2.33.0


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