linux-kernel - Re: [PATCH] powernv:idle: Set NAPSTATELOST after recovering paca on P9 DD1

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Date:   Fri, 12 May 2017 19:35:44 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        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>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powernv:idle: Set NAPSTATELOST after recovering paca on
 P9 DD1

On Fri, 12 May 2017 14:52:06 +0530
"Gautham R. Shenoy" <ego@...ux.vnet.ibm.com> wrote:

> From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
> 
> commit 17ed4c8f81da ("powerpc/powernv: Recover correct PACA on wakeup
> from a stop on P9 DD1") promises to set the NAPSTATELOST bit in paca
> after recovering the correct paca for the thread waking up from stop1
> on DD1, so that the GPRs can be correctly restored on the stop exit
> path. However, it loads the value 1 into r3, but stores the value in
> r0 into NAPSTATELOST(r13).
> 
> Fix this by correctly set the NAPSTATELOST bit in paca after
> recovering the paca on POWER9 DD1.
> 
> Fixes: commit 17ed4c8f81da ("powerpc/powernv: Recover correct PACA on wakeup
> from a stop on P9 DD1")
> 
> Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>

This looks obviously correct to me.

Reviewed-by: Nicholas Piggin <npiggin@...il.com>

> ---
>  arch/powerpc/kernel/idle_book3s.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
> index 07d4e0a..4898d67 100644
> --- a/arch/powerpc/kernel/idle_book3s.S
> +++ b/arch/powerpc/kernel/idle_book3s.S
> @@ -416,7 +416,7 @@ power9_dd1_recover_paca:
>  	 * which needs to be restored from the stack.
>  	 */
>  	li	r3, 1
> -	stb	r0,PACA_NAPSTATELOST(r13)
> +	stb	r3,PACA_NAPSTATELOST(r13)
>  	blr
>  
>  /*