linux-kernel - Re: [PATCH v4] x86/tsc: Use topology_max

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Message-ID: <Zqs70V2qVGfzFsoG@feng-clx.sh.intel.com>
Date: Thu, 1 Aug 2024 15:40:01 +0800
From: Feng Tang <feng.tang@...el.com>
To: Thomas Gleixner <tglx@...utronix.de>
CC: Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "Dave
 Hansen" <dave.hansen@...el.com>, "H . Peter Anvin" <hpa@...or.com>, "Peter
 Zijlstra" <peterz@...radead.org>, <x86@...nel.org>, <paulmck@...nel.org>,
	<rui.zhang@...el.com>, Waiman Long <longman@...hat.com>,
	<linux-kernel@...r.kernel.org>, Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v4] x86/tsc: Use topology_max_packages() to get package
 number

On Wed, Jul 31, 2024 at 08:53:11PM +0200, Thomas Gleixner wrote:
> On Mon, Jul 29 2024 at 10:12, Feng Tang wrote:
> >  	pr_info("Allowing %u present CPUs plus %u hotplug CPUs\n", assigned, disabled);
> > -	if (topo_info.nr_rejected_cpus)
> > +	if (topo_info.nr_rejected_cpus) {
> >  		pr_info("Rejected CPUs %u\n", topo_info.nr_rejected_cpus);
> > +		if (__max_logical_packages <= 4)
> > +			pr_info("TSC might be buggered due to the rejected CPUs\n");
> 
> I'm not really convinced of the value of this message.
> 
> People who limit their CPUs on the command line or at compile time
> really should know what they are doing. The kernel already tells that
> there are rejected CPUs and that extra TSC info is just annoying and
> confusing noise for people who run that and have a perfectly working TSC
> on a single/dual/quad socket machine.
> 
> I just drop that noise.
 
That makes sense to me, thanks!

Before posting the patch, I discussed this with Rui and we thought the
message was not that necessary and it was kept only in case some user
may want it. 

- Feng

> Thanks,
> 
>         tglx
> 
>