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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, dave.hansen@linux.intel.com,
	x86@kernel.org, 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
Date: Tue, 13 Jun 2023 20:53:56 +0200	[thread overview]
Message-ID: <87sfav5h2z.ffs@tglx> (raw)
In-Reply-To: <d42e9452-8210-a06a-4c91-6c2f1d038a61@linux.ibm.com>

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

  reply	other threads:[~2023-06-13 18:55 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-24 15:56 [PATCH 1/9] cpu/SMT: Move SMT prototypes into cpu_smt.h Michael Ellerman
2023-05-24 15:56 ` [PATCH 2/9] cpu/SMT: Move smt/control simple exit cases earlier Michael Ellerman
2023-05-24 15:56 ` [PATCH 3/9] cpu/SMT: Store the current/max number of threads Michael Ellerman
2023-06-10 21:26   ` Thomas Gleixner
2023-06-10 22:08     ` Thomas Gleixner
2023-06-13 17:16     ` Laurent Dufour
2023-06-13 18:53       ` Thomas Gleixner [this message]
2023-06-14 12:27         ` Laurent Dufour
2023-05-24 15:56 ` [PATCH 4/9] cpu/SMT: Create topology_smt_threads_supported() Michael Ellerman
2023-06-10 22:15   ` Thomas Gleixner
2023-05-24 15:56 ` [PATCH 5/9] cpu/SMT: Create topology_smt_thread_allowed() Michael Ellerman
2023-06-10 22:35   ` Thomas Gleixner
2023-05-24 15:56 ` [PATCH 6/9] cpu/SMT: Allow enabling partial SMT states via sysfs Michael Ellerman
2023-06-10 20:09   ` Thomas Gleixner
2023-06-10 20:13     ` Thomas Gleixner
2023-05-24 15:56 ` [PATCH 7/9] powerpc/pseries: Initialise CPU hotplug callbacks earlier Michael Ellerman
2023-05-24 15:56 ` [PATCH 8/9] powerpc: Add HOTPLUG_SMT support Michael Ellerman
2023-06-01 13:27   ` Laurent Dufour
2023-06-01 16:19     ` Laurent Dufour
2023-06-10 21:10       ` Thomas Gleixner
2023-06-12 15:20         ` Laurent Dufour
2023-06-12 16:34           ` Thomas Gleixner
2023-05-24 15:56 ` [PATCH 9/9] powerpc/pseries: Honour current SMT state when DLPAR onlining CPUs Michael Ellerman

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