From: Todd Fujinaka <todd.fujin...@intel.com>

A customer was chain-booting to provision his systems and one of the
steps was setting MFS. MFS isn't cleared by normal warm reboots
(clearing requires a GLOBR) and there was no indication of why Jumbo
Frame receives were failing.

Add a warning if MFS is set to anything lower than the default.

Signed-off-by: Todd Fujinaka <todd.fujin...@intel.com>
Tested-by: Andrew Bowers <andrewx.bow...@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirs...@intel.com>
---
 drivers/net/ethernet/intel/i40e/i40e_main.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c 
b/drivers/net/ethernet/intel/i40e/i40e_main.c
index 77a6be8ee112..2e454b0d71ee 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -15295,6 +15295,14 @@ static int i40e_probe(struct pci_dev *pdev, const 
struct pci_device_id *ent)
                        i40e_stat_str(&pf->hw, err),
                        i40e_aq_str(&pf->hw, pf->hw.aq.asq_last_status));
 
+       /* make sure the MFS hasn't been set lower than the default */
+#define MAX_FRAME_SIZE_DEFAULT 0x2600
+       val = (rd32(&pf->hw, I40E_PRTGL_SAH) &
+              I40E_PRTGL_SAH_MFS_MASK) >> I40E_PRTGL_SAH_MFS_SHIFT;
+       if (val < MAX_FRAME_SIZE_DEFAULT)
+               dev_warn(&pdev->dev, "MFS for port %x has been set below the 
default: %x\n",
+                        i, val);
+
        /* Add a filter to drop all Flow control frames from any VSI from being
         * transmitted. By doing so we stop a malicious VF from sending out
         * PAUSE or PFC frames and potentially controlling traffic for other
-- 
2.26.2

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