** Description changed:
- TBA
+ [Impact]
+
+ * Intel NICs that are SR-IOV capable and are managed by ixgbe driver presents
a potentially harmful behavior when the ixgbevf-managed VFs (Virtual Functions)
perform an ethtool link check. The ixgbevf driver issues a mailbox command in
the ethtool link state handler, which induces one IRQ in the PF (Physical
Function) per link check.
+
+ * This was reported as a sort of "denial-of-service" from a guest; due to
some link check loop running inside a guest with PCI-PT of a ixgbevf-managed
VF, the host received a huge amount of IRQs causing soft-lockups.
+
+ * The patch proposed in this SRU request fix this behavior by relying in the
saved link state (obtained in the ixgbevf's watchdog routine) instead of
issuing a mailbox command to the PF in every link state check request. The
commit is available on Linus tree: 1e1b0c658d9b ("ixgbevf: Use cached link
state instead of re-reading the value for ethtool")
+ http://git.kernel.org/linus/1e1b0c658d9b
+
+ [Test case]
+
+ Reproducing the behavior is pretty simple; having a machine with an
+ Intel NIC managed by ixgbe, proceed with the following steps:
+
+ a) Create one or more VFs
+ (echo 1 > /sys/class/net/<PF iface>/device/sriov_numvfs)
+
+ b) In a different terminal, monitor the non-TxRx PF IRQs:
+ (watch -n1 "cat /proc/interrupts | grep <PF iface> | grep -v Tx")
+
+ c) Run "ethtool <VF iface>" in a loop
+
+ Without the hereby proposed patch, the PF IRQs will increase.
+
+ [Regression potential]
+
+ The patch scope is restricted to ixgbevf ethtool link-check procedure,
+ and was developed by the vendor itself. Being a self-contained patch
+ affecting only this driver's ethtool handler, the worst potential
+ regression would be a wrong link state report.
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https://bugs.launchpad.net/bugs/1836760
Title:
ixgbe{vf} - Physical Function gets IRQ when VF checks link state
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