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Subject: Re: [PATCH 2/7] powerpc: Use TIDR CPU feature to control TIDR
 allocation
To:     "Alastair D'Silva" <alastair@au1.ibm.com>,
        linuxppc-dev@lists.ozlabs.org
Cc:     linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        mikey@neuling.org, vaibhav@linux.vnet.ibm.com,
        aneesh.kumar@linux.vnet.ibm.com, malat@debian.org,
        felix@linux.vnet.ibm.com, pombredanne@nexb.com,
        sukadev@linux.vnet.ibm.com, npiggin@gmail.com,
        gregkh@linuxfoundation.org, arnd@arndb.de,
        fbarrat@linux.vnet.ibm.com, corbet@lwn.net,
        "Alastair D'Silva" <alastair@d-silva.org>
References: <20180417020950.21446-1-alastair@au1.ibm.com>
 <20180417020950.21446-3-alastair@au1.ibm.com>
From:   Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Date:   Tue, 17 Apr 2018 14:21:10 +1000
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On 17/04/18 12:09, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@d-silva.org>
> 
> Switch the use of TIDR on it's CPU feature, rather than assuming it
> is available based on architecture.
> 
> Signed-off-by: Alastair D'Silva <alastair@d-silva.org>

There's a use of TIDR in restore_sprs() that's behind the ARCH_300 flag 
as well, ideally it should never trigger in the !P9_TIDR case, but you 
might want to update that too for clarity?

> ---
>   arch/powerpc/kernel/process.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 1237f13fed51..a3e0a3e06d5a 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1570,7 +1570,7 @@ void clear_thread_tidr(struct task_struct *t)
>   	if (!t->thread.tidr)
>   		return;
>   
> -	if (!cpu_has_feature(CPU_FTR_ARCH_300)) {
> +	if (!cpu_has_feature(CPU_FTR_P9_TIDR)) {
>   		WARN_ON_ONCE(1);
>   		return;
>   	}
> @@ -1593,7 +1593,7 @@ int set_thread_tidr(struct task_struct *t)
>   {
>   	int rc;
>   
> -	if (!cpu_has_feature(CPU_FTR_ARCH_300))
> +	if (!cpu_has_feature(CPU_FTR_P9_TIDR))
>   		return -EINVAL;
>   
>   	if (t != current)
> 

-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan@au1.ibm.com  IBM Australia Limited