linux-kernel - Re: [RFC PATCH 2/3] x86/mm: make sure LAM is up-to-date during context switching

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Message-ID: <o5t3qrrlw37hdkcja2vny3ycpmhb4dowmdj74a2wrq2x4xctqk@5g5jvzen46qe>
Date: Sat, 9 Mar 2024 18:34:38 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Yosry Ahmed <yosryahmed@...gle.com>
Cc: Dave Hansen <dave.hansen@...el.com>, Andy Lutomirski <luto@...nel.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	"Peter Zijlstra (Intel)" <peterz@...radead.org>, the arch/x86 maintainers <x86@...nel.org>, linux-mm@...ck.org, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 2/3] x86/mm: make sure LAM is up-to-date during
 context switching

On Sat, Mar 09, 2024 at 02:19:19AM +0000, Yosry Ahmed wrote:
> I don't see how skipping set_tlbstate_lam_mode() for kthreads fixes this
> problem. Do you mind elaborating?

Define what problem is.

Yes, in this scenario kthread gets more permissive LAM mode than it needs.
But nothing breaks.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov