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

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Message-ID: <20250820100812.GFaKWejCFMSAS6QIfS@fat_crate.local>
Date: Wed, 20 Aug 2025 12:08:12 +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 12:01:30PM +0200, Marcos Del Sol Vives wrote:
> Please define "once". Once per what? Per boot? Per executable? Per process?

pr_err_once(). Per boot.

> Once per boot would mean they'd need to reboot to see if any other executables
> are affected.

We'll cross that bridge when we get to it.

> (again, like IOPL emulation which was already deemed okay a couple years ago
> and merged into the kernel)

When it is flooding dmesg for no good reason, I wouldn't mind toning that down
too.

IOW, I wanna see a real, actual use case which justifies flooding dmesg. If
you don't have one, then we'll do it only when it is really warranted.

-- 
Regards/Gruss,
    Boris.

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