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From: "Ahmed S. Darwish" <darwi@linutronix.de>
To: Marcos Del Sol Vives <marcos@orca.pet>
Cc: linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>, Brian Gerst <brgerst@gmail.com>,
	Uros Bizjak <ubizjak@gmail.com>, Ard Biesheuvel <ardb@kernel.org>,
	David Kaplan <david.kaplan@amd.com>, Kees Cook <kees@kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Oleg Nesterov <oleg@redhat.com>, "Xin Li (Intel)" <xin@zytor.com>,
	Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Subject: Re: [PATCH] x86: add hintable NOPs emulation
Message-ID: <aKWj0SI1_qmT6dW2@lx-t490>
References: <20250820013452.495481-1-marcos@orca.pet>
 <aKWR8e6VUEZEgbkw@lx-t490>
 <2cd7b099-095d-405c-a7d9-b0f1f72184c2@orca.pet>
 <aKWfYo8lKmcHE14a@lx-t490>
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In-Reply-To: <aKWfYo8lKmcHE14a@lx-t490>

On Wed, 20 Aug 2025, Ahmed S. Darwish wrote:
>
> Please do:
>
>     #ifdef CONFIG_X86_HNOP_EMU
>     static bool handle_hnop(struct pt_regs *regs)
>     {
> 	// Reference 'hnop_warn' as much as you like
>     }
>     #else
>     static bool handle_hnop(struct pt_regs *regs)
>     {
> 	return false;
>     }
>     # endif
>

And as previously suggested: remove the ugly hnop_warn stuff from
'thread_struct', then you can even just do:

    static bool handle_hnop(struct pt_regs *regs)
    {
	if (!IS_ENABLED(CONFIG_X86_HNOP_EMU))
		return false;

	pr_warn_once("%s[%d] Emulating hintable NOP\n"
		     "This warning will not be repeated; even for other binaries\n"
		     current->comm, task_pid_nr(current));

	...
    }

And everything else will fit quietly in place.

--
Ahmed S. Darwish
Linutronix GmbH