linux-kernel - Re: [PATCH] x86: add hintable NOPs emulation

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Message-ID: <20250820094347.GDaKWY02hR3AAoT7la@fat_crate.local>
Date: Wed, 20 Aug 2025 11:43:47 +0200
From: Borislav Petkov <bp@...en8.de>
To: Marcos Del Sol Vives <marcos@...a.pet>
Cc: "Ahmed S. Darwish" <darwi@...utronix.de>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>, Brian Gerst <brgerst@...il.com>,
	Uros Bizjak <ubizjak@...il.com>, Ard Biesheuvel <ardb@...nel.org>,
	David Kaplan <david.kaplan@....com>, Kees Cook <kees@...nel.org>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Oleg Nesterov <oleg@...hat.com>, "Xin Li (Intel)" <xin@...or.com>,
	Sabyrzhan Tasbolatov <snovitoll@...il.com>
Subject: Re: [PATCH] x86: add hintable NOPs emulation

On Wed, Aug 20, 2025 at 11:33:05AM +0200, Marcos Del Sol Vives wrote:
> But I think the kernel should let the user know the binaries they're
> running are having some performance penalty due to this emulation, in case
> they want to recompile without the offending flags.

Sure, once perhaps.

Do you want to let the user know for each binary?

And how many users do you really think will look at dmesg and recompile their
binaries?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette