linux-kernel - Re: [1/6] powernv:idle: Correctly initialize core_idle_state

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Message-Id: <3wcSXF0gdMz9s0Z@ozlabs.org>
Date:   Tue, 30 May 2017 19:11:24 +1000 (AEST)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Michael Neuling <mikey@...ling.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [1/6] powernv:idle: Correctly initialize core_idle_state_ptr

On Tue, 2017-05-16 at 08:49:43 UTC, "Gautham R. Shenoy" wrote:
> From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
> 
> The lower 8 bits of core_idle_state_ptr tracks the number of non-idle
> threads in the core. This is supposed to be initialized to bit-map
> corresponding to the threads_per_core. However, currently it is
> initialized to PNV_CORE_IDLE_THREAD_BITS (0xFF). This is correct for
> POWER8 which has 8 threads per core, but not for POWER9 which has 4
> threads per core.
> 
> As a result, on POWER9, core_idle_state_ptr gets initialized to
> 0xFF. In case when all the threads of the core are idle, the bits
> corresponding tracking the idle-threads are non-zero. As a result, the
> idle entry/exit code fails to save/restore per-core hypervisor state
> since it assumes that there are threads in the cores which are still
> active.
> 
> Fix this by correctly initializing the lower bits of the
> core_idle_state_ptr on the basis of threads_per_core.
> 
> Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>

Series applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/5f221c3ca13dceaea8eefe21dbd85d

cheers