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Date:   Tue, 10 Oct 2023 15:10:54 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
        Fei Yang <fei.yang@intel.com>, stable@vger.kernel.org
Subject: Re: [PATCH] x86/alternatives: Disable KASAN on text_poke_early() in
 apply_alternatives()
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On Tue, Oct 10, 2023 at 12:10:56PM +0200, Peter Zijlstra wrote:
> Now, obviously you really don't want boot_cpu_has() in
> __VIRTUAL_MASK_SHIFT, that would be really bad (Linus recently
> complained about how horrible the code-gen is around this already, must
> not make it far worse).

You mean a MOV (%rip) and a TEST are so horrible there because it is
a mask?

I'd experiment with it when I get a chance...

-- 
Regards/Gruss,
    Boris.

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