Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Laurent Dufour <ldufour@linux.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        linux-kernel@vger.kernel.org
Cc:     linux-arch@vger.kernel.org, x86@kernel.org,
        dave.hansen@linux.intel.com, mingo@redhat.com, bp@alien8.de,
        linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 3/9] cpu/SMT: Store the current/max number of threads
In-Reply-To: <d42e9452-8210-a06a-4c91-6c2f1d038a61@linux.ibm.com>
References: <20230524155630.794584-1-mpe@ellerman.id.au>
 <20230524155630.794584-3-mpe@ellerman.id.au> <87fs6z80w5.ffs@tglx>
 <d42e9452-8210-a06a-4c91-6c2f1d038a61@linux.ibm.com>
Date:   Tue, 13 Jun 2023 20:53:56 +0200
Message-ID: <87sfav5h2z.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Tue, Jun 13 2023 at 19:16, Laurent Dufour wrote:
> On 10/06/2023 23:26:18, Thomas Gleixner wrote:
>> On Thu, May 25 2023 at 01:56, Michael Ellerman wrote:
>>>  #ifdef CONFIG_HOTPLUG_SMT
>>>  enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
>>> +static unsigned int cpu_smt_max_threads __ro_after_init;
>>> +unsigned int cpu_smt_num_threads;
>> 
>> Why needs this to be global? cpu_smt_control is pointlessly global already.
>
> I agree that cpu_smt_*_threads should be static.
>
> Howwever, regarding cpu_smt_control, it is used in 2 places in the x86 code:
>  - arch/x86/power/hibernate.c in arch_resume_nosmt()
>  - arch/x86/kernel/cpu/bugs.c in spectre_v2_user_select_mitigation()

Bah. I must have fatfingered the grep then.

> An accessor function may be introduced to read that value in these 2
> functions, but I'm wondering if that's really the best option.
>
> Unless there is a real need to change this through this series, I think
> cpu_smt_control can remain global.

That's fine.

Thanks,

        tglx