Re: powerpc/powernv: Clear LPCR[PECE1] via stop-api only for deep state offline

Michael Ellerman
2017-09-21T01:47:12Z

On Thu, 2017-08-31 at 11:47:41 UTC, "Gautham R. Shenoy" wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
>
> commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> stop-api only on Hotplug") clears the PECE1 bit of the LPCR via
> stop-api during CPU-Hotplug to prevent wakeup due to a decrementer on
> an offlined CPU which is in a deep stop state.
>
> In the case where the stop-api support is found to be lacking, the
> commit 785a12afdb4a ("powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT
> states when stop-api fails") disables deep states that lose hypervisor
> context. Thus in this case, the offlined CPU will be put to some
> shallow idle state.
>
> However, we currently unconditionally clear the PECE1 in LPCR via
> stop-api during CPU-Hotplug even when deep states are disabled due to
> stop-api failure.
>
> Fix this by clearing PECE1 of LPCR via stop-api during CPU-Hotplug
> *only* when the offlined CPU will be put to a deep state that loses
> hypervisor context.
>
> Fixes: commit 24be85a23d1f ("powerpc/powernv: Clear PECE1 in LPCR via
> stop-api only on Hotplug")
>
> Reported-by: Pavithra Prakash <pavirampu@linux.vnet.ibm.com>
> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> Tested-by: Pavithra Prakash <pavrampu@linux.vnet.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/5d298baa41883fc421acfd932799c0

cheers