[PATCH 1/2] cxl: Keep IRQ mappings on context teardown

[Vaibhav Jain]

Michael Neuling <mikey at neuling.org> writes:

> Keep IRQ mappings on context teardown.  This won't leak IRQs as if we
> allocate the mapping again, the generic code will give the same
> mapping used last time.
>
> Doing this works around a race in the generic code. Masking the
> interrupt introduces a race which can crash the kernel or result in
> IRQ that is never EOIed. The lost of EOI results in all subsequent
> mappings to the same HW IRQ never receiving an interrupt.
>
> We've seen this race with cxl test cases which are doing heavy context
> startup and teardown at the same time as heavy interrupt load.
>
> A fix to the generic code is being investigated also.
>
> Signed-off-by: Michael Neuling <mikey at neuling.org>
> cc: stable at vger.kernel.org # 3.8

Tested on top of following skiboot patches that fix potential races in
phb.

http://patchwork.ozlabs.org/patch/581764/
http://patchwork.ozlabs.org/patch/581765/

Tested-by: Vaibhav Jain <vaibhav at linux.vnet.ibm.com>