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From: Thomas Gleixner <tglx@linutronix.de>
To: Fenghua Yu <fenghua.yu@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	H Peter Anvin <hpa@zytor.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ravi V Shankar <ravi.v.shankar@intel.com>,
	Xiaoyao Li <xiaoyao.li@intel.com>,
	Christopherson Sean J <sean.j.christopherson@intel.com>,
	Kalle Valo <kvalo@codeaurora.org>,
	Michael Chan <michael.chan@broadcom.com>,
	linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>,
	kvm@vger.kernel.org, netdev@vger.kernel.org,
	linux-wireless@vger.kernel.org
Subject: Re: [PATCH v7 18/21] x86/clearcpuid: Support feature flag string in kernel option clearcpuid
Date: Thu, 18 Apr 2019 01:19:41 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1904180106400.3174@nanos.tec.linutronix.de> (raw)
In-Reply-To: <1555536851-17462-19-git-send-email-fenghua.yu@intel.com>

On Wed, 17 Apr 2019, Fenghua Yu wrote:

> The kernel option clearcpuid currently only takes feature bit which
> can be changed from kernel to kernel.
> 
> Extend clearcpuid to use cap flag string, which is defined in
> x86_cap_flags[] and won't be changed from kernel to kernel.
> And user can easily get the cap flag string from /proc/cpuinfo.

If your machine dies because init triggers #AC then please explain how that
easily can be read from /proc/cpuinfo and how the sysadmin can figure out
what the heck he needs to write on the kernel command line.

The whole 'clearcpuid' thing should have never been merged. It's a pure
testing/debugging thing. And no, we are not going to proliferate it and
extend it for dubious value. Quite the contrary, we should simply rip it
out.

Add a simple 'noac' or whatever command line option, which is documented
proper and can easily be mapped to a #AC crash during boot.

Thanks,

	tglx

  reply	other threads:[~2019-04-17 23:20 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-17 21:33 [PATCH v7 00/21] x86/split_lock: Enable split lock detection Fenghua Yu
2019-04-17 21:33 ` [PATCH v7 01/21] x86/common: Align cpu_caps_cleared and cpu_caps_set to unsigned long Fenghua Yu
2019-04-17 21:33 ` [PATCH v7 02/21] drivers/net/b44: Align pwol_mask to unsigned long for better performance Fenghua Yu
2019-04-17 21:33 ` [PATCH v7 03/21] wlcore: simplify/fix/optimize reg_ch_conf_pending operations Fenghua Yu
2019-04-17 21:33 ` [PATCH v7 04/21] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access Fenghua Yu
2019-04-18  9:20   ` David Laight
2019-04-18 11:08     ` David Laight
2019-04-18 11:49       ` Thomas Gleixner
2019-04-18 13:14         ` David Laight
2019-04-18 13:26           ` David Laight
2019-04-17 21:33 ` [PATCH v7 05/21] x86/msr-index: Define MSR_IA32_CORE_CAPABILITY and split lock detection bit Fenghua Yu
2019-04-17 21:33 ` [PATCH v7 06/21] x86/cpufeatures: Enumerate MSR_IA32_CORE_CAPABILITY Fenghua Yu
2019-04-17 21:33 ` [PATCH v7 07/21] x86/split_lock: Enumerate split lock detection by MSR_IA32_CORE_CAPABILITY Fenghua Yu
2019-04-17 21:33 ` [PATCH v7 08/21] x86/split_lock: Enumerate split lock detection on Icelake mobile processor Fenghua Yu
2019-04-17 21:33 ` [PATCH v7 09/21] x86/split_lock: Define MSR TEST_CTL register Fenghua Yu
2019-04-17 21:34 ` [PATCH v7 10/21] x86/split_lock: Define per CPU variable to cache MSR TEST_CTL Fenghua Yu
2019-04-17 22:14   ` Thomas Gleixner
2019-04-18  1:28     ` Fenghua Yu
2019-04-18  6:31       ` Thomas Gleixner
2019-04-17 21:34 ` [PATCH v7 11/21] x86/split_lock: Handle #AC exception for split lock Fenghua Yu
2019-04-17 21:34 ` [PATCH v7 12/21] kvm/x86: Emulate MSR IA32_CORE_CAPABILITY Fenghua Yu
2019-04-17 21:34 ` [PATCH v7 13/21] kvm/vmx: Emulate MSR TEST_CTL Fenghua Yu
2019-04-17 21:34 ` [PATCH v7 14/21] x86/split_lock: Enable split lock detection by default Fenghua Yu
2019-04-17 22:41   ` Thomas Gleixner
2019-04-17 21:34 ` [PATCH v7 15/21] x86/split_lock: Add a sysfs interface to enable/disable split lock detection during run time Fenghua Yu
2019-04-17 22:47   ` Thomas Gleixner
2019-04-18  0:57     ` Fenghua Yu
2019-04-18  6:41       ` Thomas Gleixner
2019-04-23 20:48         ` Fenghua Yu
2019-04-24 13:45           ` David Laight
2019-04-17 21:34 ` [PATCH v7 16/21] x86/split_lock: Document the new sysfs file for split lock detection Fenghua Yu
2019-04-17 21:34 ` [PATCH v7 17/21] x86/clearcpuid: Support multiple clearcpuid options Fenghua Yu
2019-04-17 23:05   ` Thomas Gleixner
2019-04-17 21:34 ` [PATCH v7 18/21] x86/clearcpuid: Support feature flag string in kernel option clearcpuid Fenghua Yu
2019-04-17 23:19   ` Thomas Gleixner [this message]
2019-04-17 23:47     ` Fenghua Yu
2019-04-18  6:16       ` Thomas Gleixner
2019-04-17 21:34 ` [PATCH v7 19/21] x86/clearcpuid: Apply cleared feature bits that are forced set before Fenghua Yu
2019-04-17 21:34 ` [PATCH v7 20/21] x86/clearcpuid: Clear CPUID bit in CPUID faulting Fenghua Yu
2019-04-17 21:34 ` [PATCH v7 21/21] x86/clearcpuid: Change document for kernel option clearcpuid Fenghua Yu

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