From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>,
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, Peter Zijlstra <peterz@infradead.org>,
Josh Poimboeuf <jpoimboe@kernel.org>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>
Subject: Re: [PATCH 1/3] x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n
Date: Mon, 15 Apr 2024 13:13:36 +0200 [thread overview]
Message-ID: <CAMuHMdVjB2g+fN8dxcmHUjKhzDChPpwcf8hMCbf=arOK5MkOuQ@mail.gmail.com> (raw)
In-Reply-To: <20240409175108.1512861-2-seanjc@google.com>
Hi Sean,
On Tue, Apr 9, 2024 at 7:51 PM Sean Christopherson <seanjc@google.com> wrote:
> Initialize cpu_mitigations to CPU_MITIGATIONS_OFF if the kernel is built
> with CONFIG_SPECULATION_MITIGATIONS=n, as the help text quite clearly
> states that disabling SPECULATION_MITIGATIONS is supposed to turn off all
> mitigations by default.
>
> │ If you say N, all mitigations will be disabled. You really
> │ should know what you are doing to say so.
>
> As is, the kernel still defaults to CPU_MITIGATIONS_AUTO, which results in
> some mitigations being enabled in spite of SPECULATION_MITIGATIONS=n.
>
> Fixes: f43b9876e857 ("x86/retbleed: Add fine grained Kconfig knobs")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sean Christopherson <seanjc@google.com>
Thanks for your patch, which is now commit f337a6a21e2fd67e
("x86/cpu: Actually turn off mitigations by default
for SPECULATION_MITIGATIONS=n") in v6.9-rc4.
This causes the following suspicious messages on R-Car H3:
CPU features: kernel page table isolation forced OFF by mitigations=off
spectre-v4 mitigation disabled by command-line option
spectre-v2 mitigation disabled by command line option
spectre-v2 mitigation disabled by command line option
and R-Car V4H:
CPU features: kernel page table isolation forced OFF by mitigations=off
spectre-v4 mitigation disabled by command-line option
spectre-bhb mitigation disabled by command line option
spectre-bhb mitigation disabled by command line option
Interestingly, no mitigations are disabled on the command-line.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
next parent reply other threads:[~2024-04-15 11:13 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240409175108.1512861-1-seanjc@google.com>
[not found] ` <20240409175108.1512861-2-seanjc@google.com>
2024-04-15 11:13 ` Geert Uytterhoeven [this message]
[not found] ` <20240413115324.53303a68@canb.auug.org.au>
[not found] ` <87edb9d33r.fsf@mail.lhotse>
[not found] ` <87bk6dd2l4.fsf@mail.lhotse>
2024-04-15 11:16 ` [PATCH 1/3] x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n Geert Uytterhoeven
2024-04-15 14:31 ` Sean Christopherson
2024-04-16 11:06 ` Michael Ellerman
2024-04-19 14:03 ` Will Deacon
2024-04-19 14:06 ` Sean Christopherson
2024-04-19 14:38 ` Will Deacon
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