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From: Michael Ellerman <mpe@ellerman.id.au>
To: Stephen Rothwell <sfr@canb.auug.org.au>,
	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>,
	linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Heiko Carstens <hca@linux.ibm.com>
Subject: Re: [PATCH 1/3] x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n
Date: Sat, 13 Apr 2024 19:38:47 +1000	[thread overview]
Message-ID: <87bk6dd2l4.fsf@mail.lhotse> (raw)
In-Reply-To: <87edb9d33r.fsf@mail.lhotse>

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

cheers

WARNING: multiple messages have this Message-ID (diff)
From: Michael Ellerman <mpe@ellerman.id.au>
To: Stephen Rothwell <sfr@canb.auug.org.au>,
	Sean Christopherson <seanjc@google.com>
Cc: linux-arch@vger.kernel.org, x86@kernel.org,
	Will Deacon <will@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	linuxppc-dev@lists.ozlabs.org,
	Josh Poimboeuf <jpoimboe@kernel.org>,
	Daniel Sneddon <daniel.sneddon@linux.intel.com>
Subject: Re: [PATCH 1/3] x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n
Date: Sat, 13 Apr 2024 19:38:47 +1000	[thread overview]
Message-ID: <87bk6dd2l4.fsf@mail.lhotse> (raw)
In-Reply-To: <87edb9d33r.fsf@mail.lhotse>

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

cheers

  reply	other threads:[~2024-04-13  9:38 UTC|newest]

Thread overview: 30+ 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
2024-04-10 14:31   ` [tip: x86/urgent] " tip-bot2 for Sean Christopherson
2024-04-13  1:53   ` [PATCH 1/3] " Stephen Rothwell
2024-04-13  1:53     ` Stephen Rothwell
2024-04-13  9:27     ` Michael Ellerman
2024-04-13  9:27       ` Michael Ellerman
2024-04-13  9:38       ` Michael Ellerman [this message]
2024-04-13  9:38         ` Michael Ellerman
2024-04-14 22:42         ` Stephen Rothwell
2024-04-14 22:42           ` Stephen Rothwell
2024-04-15 11:16         ` Geert Uytterhoeven
2024-04-15 11:16           ` Geert Uytterhoeven
2024-04-15 14:31           ` Sean Christopherson
2024-04-15 14:31             ` Sean Christopherson
2024-04-16 11:06             ` Michael Ellerman
2024-04-16 11:06               ` Michael Ellerman
2024-04-19 14:03             ` Will Deacon
2024-04-19 14:03               ` Will Deacon
2024-04-19 14:06               ` Sean Christopherson
2024-04-19 14:06                 ` Sean Christopherson
2024-04-19 14:38                 ` Will Deacon
2024-04-19 14:38                   ` Will Deacon
2024-04-15 11:13   ` Geert Uytterhoeven
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
2024-04-10 14:31   ` [tip: x86/urgent] " tip-bot2 for 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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