From: Will Deacon <will@kernel.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Stephen Rothwell <sfr@canb.auug.org.au>,
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>,
linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org,
Catalin Marinas <catalin.marinas@arm.com>,
Heiko Carstens <hca@linux.ibm.com>,
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: Fri, 19 Apr 2024 15:03:22 +0100 [thread overview]
Message-ID: <20240419140321.GF3148@willie-the-truck> (raw)
In-Reply-To: <Zh06O35yKIF2vNdE@google.com>
On Mon, Apr 15, 2024 at 07:31:23AM -0700, Sean Christopherson wrote:
> On Mon, Apr 15, 2024, Geert Uytterhoeven wrote:
> > On Sat, Apr 13, 2024 at 11:38 AM Michael Ellerman <mpe@ellerman.id.au> wrote:
> > > Michael Ellerman <mpe@ellerman.id.au> writes:
> > > > Stephen Rothwell <sfr@canb.auug.org.au> writes:
> > > ...
> > > >> On Tue, 9 Apr 2024 10:51:05 -0700 Sean Christopherson <seanjc@google.com> wrote:
> > > ...
> > > >>> diff --git a/kernel/cpu.c b/kernel/cpu.c
> > > >>> index 8f6affd051f7..07ad53b7f119 100644
> > > >>> --- a/kernel/cpu.c
> > > >>> +++ b/kernel/cpu.c
> > > >>> @@ -3207,7 +3207,8 @@ enum cpu_mitigations {
> > > >>> };
> > > >>>
> > > >>> static enum cpu_mitigations cpu_mitigations __ro_after_init =
> > > >>> - CPU_MITIGATIONS_AUTO;
> > > >>> + IS_ENABLED(CONFIG_SPECULATION_MITIGATIONS) ? CPU_MITIGATIONS_AUTO :
> > > >>> + CPU_MITIGATIONS_OFF;
> > > >>>
> > > >>> static int __init mitigations_parse_cmdline(char *arg)
> > > >>> {
> > >
> > > I think a minimal workaround/fix would be:
> > >
> > > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> > > index 2b8fd6bb7da0..290be2f9e909 100644
> > > --- a/drivers/base/Kconfig
> > > +++ b/drivers/base/Kconfig
> > > @@ -191,6 +191,10 @@ config GENERIC_CPU_AUTOPROBE
> > > config GENERIC_CPU_VULNERABILITIES
> > > bool
> > >
> > > +config SPECULATION_MITIGATIONS
> > > + def_bool y
> > > + depends on !X86
> > > +
> > > config SOC_BUS
> > > bool
> > > select GLOB
> >
> > Thanks, that works for me (on arm64), so
> > Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
>
> Oof. I completely missed that "cpu_mitigations" wasn't x86-only. I can't think
> of better solution than an on-by-default generic Kconfig, though can't that it
> more simply be:
>
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index 2b8fd6bb7da0..5930cb56ee29 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -191,6 +191,9 @@ config GENERIC_CPU_AUTOPROBE
> config GENERIC_CPU_VULNERABILITIES
> bool
>
> +config SPECULATION_MITIGATIONS
> + def_bool !X86
> +
> config SOC_BUS
> bool
> select GLOB
I can't see this in -next yet. Do you plan to post it as a proper patch
to collect acks etc?
Cheers,
Will
next prev parent reply other threads:[~2024-04-19 14:03 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-09 17:51 [PATCH 0/3] x86/cpu: Fix SPECULATIVE_MITIGATION=n kernels Sean Christopherson
2024-04-09 17:51 ` [PATCH 1/3] x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n Sean Christopherson
2024-04-13 1:53 ` Stephen Rothwell
2024-04-13 9:27 ` Michael Ellerman
2024-04-13 9:38 ` Michael Ellerman
2024-04-14 22:42 ` Stephen Rothwell
2024-04-15 11:16 ` Geert Uytterhoeven
2024-04-15 14:31 ` Sean Christopherson
2024-04-16 11:06 ` Michael Ellerman
2024-04-19 14:03 ` Will Deacon [this message]
2024-04-19 14:06 ` Sean Christopherson
2024-04-19 14:38 ` Will Deacon
2024-04-15 11:13 ` Geert Uytterhoeven
2024-04-09 17:51 ` [PATCH 2/3] x86/cpu: Disable BHI mitigation by default when SPECULATION_MITIGATIONS=n Sean Christopherson
2024-04-09 17:51 ` [PATCH 3/3] x86/cpu: Ignore "mitigations" kernel parameter if SPECULATION_MITIGATIONS=n Sean Christopherson
2024-04-10 14:18 ` Ingo Molnar
2024-04-09 18:55 ` [PATCH 0/3] x86/cpu: Fix SPECULATIVE_MITIGATION=n kernels Daniel Sneddon
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