Samuel Mendoza-Jonas [off-list ref] writes:

Commit 2def86a7200c
("hvc: Convert to using interrupts instead of opal events")
enabled the use of interrupts in the hvc_driver for OPAL platforms.
However on machines with more than one hvc console, any console after
the first will fail to register an interrupt handler in
notifier_add_irq() since all consoles share the same IRQ number but do
not set the IRQF_SHARED flag:

[   51.179907] genirq: Flags mismatch irq 31. 00000000 (hvc_console) vs.
00000000 (hvc_console)
[   51.180010] hvc_open: request_irq failed with rc -16.

This error propagates up to hvc_open() and the console is closed, but
OPAL will still generate interrupts that are not handled, leading to
rcu_sched stall warnings.

Set IRQF_SHARED when calling request_irq, allowing additional consoles
to start properly.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Cc: <redacted> # 4.1.x-

Tested on 4.4.6 - seemed to stop (some of) the problems I was having
when using it as a kernel for the bootloader on a FSP based POWER8
system.

Tested-by: Stewart Smith <redacted>

-- 
Stewart Smith
OPAL Architect, IBM.