linux-kernel - Re: [RFC PATCH 1/3] x86/mm: fix LAM cr3 mask inconsistency during context switch

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Date: Thu, 7 Mar 2024 15:21:26 -0800
From: Yosry Ahmed <yosryahmed@...gle.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Peter Zijlstra <peterz@...radead.org>, 
	Andy Lutomirski <luto@...nel.org>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, x86@...nel.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/3] x86/mm: fix LAM cr3 mask inconsistency during
 context switch

> > The "set_" naming bugs me in both of the sites that get modified here.
> > I'd be with a new name that fits better, if we can think of one.
>
> Is it because it's not clear we are updating cpu_tlbstate (in which case
> I think update_cpu_tlbstate_lam() is an improvement), or is it because
> the function returns a value now? If the latter we can put "return" in
> the name somewhere, or keep the function void and pass in an output
> parameter.

Or we can avoid returning a value from the helper and avoid passing an
mm. The callers would be more verbose, they'll have to call
mm_lam_cr3_mask() and mm_untag_mask() and pass the results into the
helper (set_tlbstate_lam_mode() or update_cpu_tlbstate_lam()). Another
advantage of this is that we can move the READ_ONCE to
switch_mm_irqs_off() and keep the comment here.

WDYT?