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Re: [v3, 1/2] powernv/powerpc:Save/Restore additional SPRs for stop4 cpuidle

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  Re: [v3, 1/2] powernv/powerpc:Save/Restore additional SPRs for stop4 cpuidle Michael Ellerman <patch-notifications@ellerman.id.au> - 2017-08-07 12:50 +0200

#1705341 — Re: [v3, 1/2] powernv/powerpc:Save/Restore additional SPRs for stop4 cpuidle

On Fri, 2017-07-21 at 10:41:37 UTC, "Gautham R. Shenoy" wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> 
> The stop4 idle state on POWER9 is a deep idle state which loses
> hypervisor resources, but whose latency is low enough that it can be
> exposed via cpuidle.
> 
> Until now, the deep idle states which lose hypervisor resources (eg:
> winkle) were only exposed via CPU-Hotplug.  Hence currently on wakeup
> from such states, barring a few SPRs which need to be restored to
> their older value, rest of the SPRS are reinitialized to their values
> corresponding to that at boot time.
> 
> When stop4 is used in the context of cpuidle, we want these additional
> SPRs to be restored to their older value, to ensure that the context
> on the CPU coming back from idle is same as it was before going idle.
> 
> In this patch, we define a SPR save area in PACA (since we have used
> up the volatile register space in the stack) and on POWER9, we restore
> SPRN_PID, SPRN_LDBAR, SPRN_FSCR, SPRN_HFSCR, SPRN_MMCRA, SPRN_MMCR1,
> SPRN_MMCR2 to the values they had before entering stop.
> 
> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

Series applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/e1c1cfed54326fd2b17c78f0c85092

cheers

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