linux-kernel - Re: [PATCH v14 11/13] x86/mm: do targeted broadcast flushing from tlbbatch code

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Message-ID: <Z8b3n85dpkz_-2ci@google.com>
Date: Tue, 4 Mar 2025 12:52:47 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Borislav Petkov <bp@...en8.de>, Rik van Riel <riel@...riel.com>,
	x86@...nel.org, linux-kernel@...r.kernel.org, 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@....com, mingo@...nel.org
Subject: Re: [PATCH v14 11/13] x86/mm: do targeted broadcast flushing from
 tlbbatch code

On Mon, Mar 03, 2025 at 01:47:42PM -0800, Dave Hansen wrote:
> >  static void broadcast_tlb_flush(struct flush_tlb_info *info)
> >  {
> >  	bool pmd = info->stride_shift == PMD_SHIFT;
> > @@ -790,6 +821,8 @@ void switch_mm_irqs_off(struct mm_struct *unused, struct mm_struct *next,
> >  	if (IS_ENABLED(CONFIG_PROVE_LOCKING))
> >  		WARN_ON_ONCE(!irqs_disabled());
> >  
> > +	tlbsync();
> 
> This one is in dire need of comments.

I have been advocating to move this to a place where it's clearer. I
also think it needs comments:

https://lore.kernel.org/all/CA+i-1C31TrceZiizC_tng_cc-zcvKsfXLAZD_XDftXnp9B2Tdw@mail.gmail.com/