linux-kernel - Re: [PATCH v11 09/12] x86/mm: enable broadcast TLB invalidation for multi-threaded processes

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Message-ID: <CA+i-1C2G9Db1X+qa3FrYSDFZmQJoms=VBpBpVPyQbCX17djYow@mail.gmail.com>
Date: Mon, 17 Feb 2025 14:22:08 +0100
From: Brendan Jackman <jackmanb@...gle.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Rik van Riel <riel@...riel.com>, x86@...nel.org, linux-kernel@...r.kernel.org, 
	bp@...en8.de, peterz@...radead.org, dave.hansen@...ux.intel.com, 
	zhengqi.arch@...edance.com, nadav.amit@...il.com, thomas.lendacky@....com, 
	kernel-team@...a.com, linux-mm@...ck.org, akpm@...ux-foundation.org, 
	jannh@...gle.com, mhklinux@...look.com, andrew.cooper3@...rix.com, 
	Manali Shukla <Manali.Shukla@....com>
Subject: Re: [PATCH v11 09/12] x86/mm: enable broadcast TLB invalidation for
 multi-threaded processes

On Fri, 14 Feb 2025 at 20:53, Dave Hansen <dave.hansen@...el.com> wrote:
> > +     /*
> > +      * TLB consistency for global ASIDs is maintained with broadcast TLB
> > +      * flushing. The TLB is never outdated, and does not need flushing.
> > +      */
>
> This is another case where I think using the word "broadcast" is not
> helping.
>
> Here's the problem: INVLPGB is a "INVLPG" that's broadcast. So the name
> INVLPGB is fine. INVLPGB is *a* way to broadcast INVLPG which is *a*
> kind of TLB invalidation.
>
> But, to me "broadcast TLB flushing" is a broad term. In arguably
> includes INVLPGB and normal IPI-based flushing. Just like the function
> naming in the earlier patch, I think we need a better term here.

If we wanna refer to invlpgb-type things without saying invlpgb, and
as you pointed out "broadcast" is too general, I think we just need
the terminology to refer to the fact it's a special "hardware"
feature.

So "hardware-synchronized" or something like that. The former would
abbrev to hwsync in identifiers, without any loss of clarity.