From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Kirsher Subject: [net-next 17/25] fm10k: comment next_vf_mbx flow Date: Tue, 14 Apr 2015 16:51:03 -0700 Message-ID: <1429055471-401-18-git-send-email-jeffrey.t.kirsher@intel.com> References: <1429055471-401-1-git-send-email-jeffrey.t.kirsher@intel.com> Cc: Jeff Kirsher , netdev@vger.kernel.org, nhorman@redhat.com, sassmann@redhat.com, jogreene@redhat.com, Jacob Keller To: davem@davemloft.net Return-path: Received: from mga11.intel.com ([192.55.52.93]:20409 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754928AbbDNXvZ (ORCPT ); Tue, 14 Apr 2015 19:51:25 -0400 In-Reply-To: <1429055471-401-1-git-send-email-jeffrey.t.kirsher@intel.com> Sender: netdev-owner@vger.kernel.org List-ID: Add a header comment explaining why we have the somewhat crazy mailbox flow. This flow is necessary as it prevents the PF<->SM mailbox from being flooded by the VF messages, which normally trigger a message to the PF. This helps prevent the case where we see a PF mailbox timeout. Signed-off-by: Jeff Kirsher Signed-off-by: Jacob Keller Acked-by: Matthew Vick Tested-by: Krishneil Singh --- drivers/net/ethernet/intel/fm10k/fm10k_iov.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_iov.c b/drivers/net/ethernet/intel/fm10k/fm10k_iov.c index 0b37e19..5b08e62 100644 --- a/drivers/net/ethernet/intel/fm10k/fm10k_iov.c +++ b/drivers/net/ethernet/intel/fm10k/fm10k_iov.c @@ -113,6 +113,13 @@ s32 fm10k_iov_mbx(struct fm10k_intfc *interface) /* lock the mailbox for transmit and receive */ fm10k_mbx_lock(interface); + /* Most VF messages sent to the PF cause the PF to respond by + * requesting from the SM mailbox. This means that too many VF + * messages processed at once could cause a mailbox timeout on the PF. + * To prevent this, store a pointer to the next VF mbx to process. Use + * that as the start of the loop so that we don't starve whichever VF + * got ignored on the previous run. + */ process_mbx: for (i = iov_data->next_vf_mbx ? : iov_data->num_vfs; i--;) { struct fm10k_vf_info *vf_info = &iov_data->vf_info[i]; @@ -137,6 +144,10 @@ process_mbx: mbx->ops.process(hw, mbx); } + /* if we stopped processing mailboxes early, update next_vf_mbx. + * Otherwise, reset next_vf_mbx, and restart loop so that we process + * the remaining mailboxes we skipped at the start. + */ if (i >= 0) { iov_data->next_vf_mbx = i + 1; } else if (iov_data->next_vf_mbx) { -- 1.9.3