From: Peter Zijlstra <peterz@infradead.org>
To: Borislav Petkov <bp@alien8.de>
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()
Date: Tue, 10 Oct 2023 15:54:56 +0200 [thread overview]
Message-ID: <20231010135456.GL377@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20231010131054.GHZSVNXhruJIx0iCzq@fat_crate.local>
On Tue, Oct 10, 2023 at 03:10:54PM +0200, Borislav Petkov wrote:
> 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...
That gets you a memory-reference and potential cachemiss what should
have been an immediate :/
prev parent reply other threads:[~2023-10-10 13:55 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-10 5:37 [PATCH] x86/alternatives: Disable KASAN on text_poke_early() in apply_alternatives() Kirill A. Shutemov
2023-10-10 8:19 ` Borislav Petkov
2023-10-10 8:40 ` Kirill A. Shutemov
2023-10-10 9:12 ` Borislav Petkov
2023-10-10 10:24 ` Kirill A. Shutemov
2023-10-10 10:10 ` Peter Zijlstra
2023-10-10 10:16 ` Peter Zijlstra
2023-10-10 10:30 ` Kirill A. Shutemov
2023-10-10 10:25 ` Kirill A. Shutemov
2023-10-10 11:24 ` Peter Zijlstra
2023-10-10 13:10 ` Borislav Petkov
2023-10-10 13:54 ` Peter Zijlstra [this message]
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