** Also affects: linux (Ubuntu Xenial)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1703663
Title:
ISST-LTE: Briggs:Stratton:UbuntuKVM: ics_opal_set_affinity on host
kernel log using Intel X710 (i40e driver)
Status in The Ubuntu-power-systems project:
New
Status in linux package in Ubuntu:
New
Status in linux source package in Xenial:
New
Bug description:
SRU Justification:
Impact:
We have an issue with the i40e driver, present in kernels pre-4.8, like
Xenial v4.4 (from Ubuntu 16.04.1).
i40e driver has an issue in interrupt vector assignment in case of
sparse CPU masks, like when some CPUs are disabled. The driver does a
linear mapping not taking gaps on cpumask into account. This is a
problem in systems with multiple logical CPUs per core (like in SMT
scenarios).
If we disable some logical CPUs, by turning SMT off for example, we
will end up with a sparse cpu_online_mask, i.e., only the first CPU in
a core is online, and the incremental/linear filling in the interrupt
cpumask might lead to multiple offline CPUs being assigned to the
struct q_vector in the driver, leading to issues when interrupts are
requested, like the following message in PowerPC systems:
[141.97] ics_opal_set_affinity: No online cpus in the mask
00200000,00000000,00000000,00000000 for irq 302
This message is output of interrupt controller in Power systems, a
complain that the cpumask does not make sense to that particular
system.
Fix: Cherry-picking 7f6c553902bfa1c4e3f6cfa955c5ea036c7fe8e4
i40e: use valid online CPU on q_vector initialization
into Xenial. Change limited to specific driver. Regression potential should
be low and results testable.
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