From: Thomas Gleixner <tglx@linutronix.de>
To: Fenghua Yu <fenghua.yu@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>, H Peter Anvin <hpa@zytor.com>,
Dave Hansen <dave.hansen@intel.com>,
Ashok Raj <ashok.raj@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Michael Chan <michael.chan@broadcom.com>,
Ravi V Shankar <ravi.v.shankar@intel.com>,
Ricardo Neri <ricardo.neri@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
Subject: Re: [PATCH v3 08/10] x86/setcpuid: Add kernel option setcpuid
Date: Mon, 4 Feb 2019 17:49:06 +0000 (GMT) [thread overview]
Message-ID: <alpine.DEB.2.21.1902041745370.3006@nanos.tec.linutronix.de> (raw)
In-Reply-To: <1549084491-57808-9-git-send-email-fenghua.yu@intel.com>
On Fri, 1 Feb 2019, Fenghua Yu wrote:
> On some platforms, a feature (e.g. #AC for split lock) may not be
> enumerated by CPUID or non architectural way in IA32_CORE_CAPABILITY.
> To enable the feature on the platforms, a new kernel option setcpuid
> is added.
>
> The feature is defined in cpufeatures.h. The kernel option setcpuid
> takes either feature bit or cpu cap flag corresponding to the feature.
> The format of the option:
> setcpuid=<feature bit>
> setcpuid=<feature capability flag>
>
> Check cpufeatures.h for valid feature bit numbers and check capflags.c
> or /proc/cpuinfo for valid feature capability flags.
>
> Enabling multiple features are supported.
>
> Please note kernel may malfunction if some features are enabled by
> the option.
>
> This option behaves like existing kernel option clearcpuid.
No it does NOT. clearcpuid allows to disable things.
This allows to enable random CPUID bits without any sanity checking. Not
going to happen. We made it clear in the past that functionality needs to
be detectable by enumeration. We do quirks for broken crap, but this is
just not how it works.
Thanks,
tglx
next prev parent reply other threads:[~2019-02-04 17:49 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-02 5:14 [PATCH v3 00/10] x86/split_lock: Enable #AC exception for split locked accesses Fenghua Yu
2019-02-02 5:14 ` [PATCH v3 01/10] x86/common: Align cpu_caps_cleared and cpu_caps_set to unsigned long Fenghua Yu
2019-02-02 5:14 ` [PATCH v3 02/10] drivers/net/b44: Align pwol_mask to unsigned long for better performance Fenghua Yu
2019-02-02 5:14 ` [PATCH v3 03/10] wlcore: Align reg_ch_conf_pending and tmp_ch_bitmap " Fenghua Yu
2019-02-02 5:14 ` [PATCH v3 04/10] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access Fenghua Yu
2019-02-02 5:14 ` [PATCH v3 05/10] x86/clearcpuid: Support multiple clearcpuid options Fenghua Yu
2019-02-02 5:14 ` [PATCH v3 06/10] x86/clearcpuid: Support feature flag string in kernel option clearcpuid Fenghua Yu
2019-02-02 5:14 ` [PATCH v3 07/10] Change document for " Fenghua Yu
2019-02-02 5:14 ` [PATCH v3 08/10] x86/setcpuid: Add kernel option setcpuid Fenghua Yu
2019-02-04 17:49 ` Thomas Gleixner [this message]
2019-02-04 19:05 ` Dave Hansen
2019-02-04 19:57 ` Borislav Petkov
2019-02-04 20:46 ` Dave Hansen
2019-02-04 21:40 ` Borislav Petkov
2019-02-04 22:14 ` Fenghua Yu
2019-02-05 6:10 ` Borislav Petkov
2019-02-04 23:24 ` Dave Hansen
2019-02-05 6:18 ` Borislav Petkov
2019-02-05 16:46 ` Dave Hansen
2019-02-05 17:09 ` Peter Zijlstra
2019-02-05 8:57 ` Peter Zijlstra
2019-02-05 13:15 ` Peter Zijlstra
2019-02-05 8:48 ` Peter Zijlstra
2019-02-05 15:19 ` Dave Hansen
2019-02-05 15:43 ` Borislav Petkov
2019-02-05 18:26 ` Fenghua Yu
2019-02-05 17:04 ` Peter Zijlstra
2019-02-10 19:20 ` Thomas Gleixner
2019-02-11 19:16 ` Fenghua Yu
2019-02-12 13:37 ` Peter Zijlstra
2019-02-12 13:51 ` Thomas Gleixner
2019-02-12 16:48 ` Peter Zijlstra
2019-02-12 16:50 ` Dave Hansen
2019-02-12 17:52 ` Yu, Fenghua
2019-02-04 21:09 ` Fenghua Yu
2019-02-05 8:51 ` Peter Zijlstra
2019-02-05 15:21 ` Dave Hansen
2019-02-05 15:34 ` Peter Zijlstra
2019-02-02 5:14 ` [PATCH v3 09/10] x86/split_lock: Define #AC for split lock feature Fenghua Yu
2019-02-04 18:41 ` Dave Hansen
2019-02-04 18:45 ` Fenghua Yu
2019-02-04 19:00 ` Dave Hansen
2019-02-04 19:03 ` Fenghua Yu
2019-02-02 5:14 ` [PATCH v3 10/10] x86/split_lock: Handle #AC exception for split lock Fenghua Yu
2019-02-04 11:00 ` kbuild test robot
2019-02-04 14:43 ` kbuild test robot
2019-02-11 10:53 ` Ingo Molnar
2019-02-11 18:10 ` Fenghua Yu
2019-02-13 8:14 ` Ingo Molnar
2019-02-13 14:37 ` Yu, Fenghua
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