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From: Fenghua Yu <fenghua.yu@intel.com>
To: "Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>, "H Peter Anvin" <hpa@zytor.com>,
	"Dave Hansen" <dave.hansen@intel.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Ashok Raj" <ashok.raj@intel.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Kalle Valo" <kvalo@codeaurora.org>,
	"Xiaoyao Li " <xiaoyao.li@intel.com>,
	"Michael Chan" <michael.chan@broadcom.com>,
	"Ravi V Shankar" <ravi.v.shankar@intel.com>
Cc: "linux-kernel" <linux-kernel@vger.kernel.org>,
	"x86" <x86@kernel.org>,
	linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
	kvm@vger.kernel.org, Fenghua Yu <fenghua.yu@intel.com>
Subject: [PATCH v6 20/20] x86/clearcpuid: Change document for kernel option clearcpuid
Date: Wed,  3 Apr 2019 14:22:06 -0700	[thread overview]
Message-ID: <1554326526-172295-21-git-send-email-fenghua.yu@intel.com> (raw)
In-Reply-To: <1554326526-172295-1-git-send-email-fenghua.yu@intel.com>

Since kernel option clearcpuid now supports multiple options and CPU
capability flags, the document needs to be changed.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
---
 .../admin-guide/kernel-parameters.txt          | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 2b8ee90bb644..0cbeda6d7f16 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -563,17 +563,21 @@
 			loops can be debugged more effectively on production
 			systems.
 
-	clearcpuid=BITNUM [X86]
+	clearcpuid=BITNUM | FLAG [X86]
 			Disable CPUID feature X for the kernel. See
 			arch/x86/include/asm/cpufeatures.h for the valid bit
-			numbers. Note the Linux specific bits are not necessarily
+			numbers or /proc/cpuinfo for valid CPU flags.
+			Multiple options can be used to disable a few features.
+			This prevents the feature from being used by the
+			kernel or shown in /proc/cpuinfo or shown in CPUID
+			called directly by user programs.
+			A few notes:
+			- The Linux specific bits are not necessarily
 			stable over kernel options, but the vendor specific
 			ones should be.
-			Also note that user programs calling CPUID directly
-			or using the feature without checking anything
-			will still see it. This just prevents it from
-			being used by the kernel or shown in /proc/cpuinfo.
-			Also note the kernel might malfunction if you disable
+			- User programs using the feature without checking
+			anything will still use it.
+			- The kernel might malfunction if you disable
 			some critical bits.
 
 	cma=nn[MG]@[start[MG][-end[MG]]]
-- 
2.19.1


      parent reply	other threads:[~2019-04-03 21:30 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-03 21:21 [PATCH v6 00/20] x86/split_lock: Enable split locked accesses detection Fenghua Yu
2019-04-03 21:21 ` [PATCH v6 01/20] x86/common: Align cpu_caps_cleared and cpu_caps_set to unsigned long Fenghua Yu
2019-04-04 14:39   ` Borislav Petkov
2019-04-04 15:54     ` Fenghua Yu
2019-04-03 21:21 ` [PATCH v6 02/20] drivers/net/b44: Align pwol_mask to unsigned long for better performance Fenghua Yu
2019-04-03 21:21 ` [PATCH v6 03/20] wlcore: simplify/fix/optimize reg_ch_conf_pending operations Fenghua Yu
2019-04-03 21:21 ` [PATCH v6 04/20] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access Fenghua Yu
2019-04-04 14:44   ` David Laight
2019-04-04 16:24     ` David Laight
2019-04-04 16:35       ` Sean Christopherson
2019-04-04 16:35         ` Sean Christopherson
2019-04-04 16:52       ` Thomas Gleixner
2019-04-04 17:29         ` Paolo Bonzini
2019-04-04 18:11           ` Thomas Gleixner
2019-04-05  9:23         ` David Laight
2019-04-03 21:21 ` [PATCH v6 05/20] x86/msr-index: Define MSR_IA32_CORE_CAPABILITY and split lock detection bit Fenghua Yu
2019-04-03 21:21 ` [PATCH v6 06/20] x86/cpufeatures: Enumerate MSR_IA32_CORE_CAPABILITY Fenghua Yu
2019-04-03 21:21 ` [PATCH v6 07/20] x86/split_lock: Enumerate split lock detection by MSR_IA32_CORE_CAPABILITY Fenghua Yu
2019-04-03 21:21 ` [PATCH v6 08/20] x86/split_lock: Enumerate split lock detection on Icelake mobile processor Fenghua Yu
2019-04-03 21:21 ` [PATCH v6 09/20] x86/split_lock: Define MSR_TEST_CTL register Fenghua Yu
2019-04-03 21:21 ` [PATCH v6 10/20] x86/split_lock: Handle #AC exception for split lock Fenghua Yu
2019-04-04 17:31   ` Thomas Gleixner
2019-04-04 22:49     ` Fenghua Yu
2019-04-03 21:21 ` [PATCH v6 11/20] kvm/x86: Emulate MSR IA32_CORE_CAPABILITY Fenghua Yu
2019-04-05 12:00   ` Thomas Gleixner
2019-04-09  6:03     ` Xiaoyao Li
2019-04-03 21:21 ` [PATCH v6 12/20] kvm/vmx: Emulate MSR TEST_CTL Fenghua Yu
2019-04-04 14:44   ` Sean Christopherson
2019-04-08  8:54     ` Xiaoyao Li
2019-04-05 12:30   ` Thomas Gleixner
2019-04-08  9:54     ` Xiaoyao Li
2019-04-08 17:48       ` Sean Christopherson
2019-04-10  5:03         ` Xiaoyao Li
2019-04-03 21:21 ` [PATCH v6 13/20] x86/split_lock: Enable split lock detection by default Fenghua Yu
2019-04-04 18:07   ` Thomas Gleixner
2019-04-04 18:14     ` Thomas Gleixner
2019-04-04 19:23     ` Fenghua Yu
2019-04-04 19:44       ` Thomas Gleixner
2019-04-10  0:02     ` Fenghua Yu
2019-04-10  6:31       ` Thomas Gleixner
2019-04-10 12:35         ` Fenghua Yu
2019-04-10  8:50       ` David Laight
2019-04-03 21:22 ` [PATCH v6 14/20] x86/split_lock: Add a sysfs interface to enable/disable split lock detection during run time Fenghua Yu
2019-04-04 19:11   ` Thomas Gleixner
2019-04-03 21:22 ` [PATCH v6 15/20] x86/split_lock: Document the new sysfs file for split lock detection Fenghua Yu
2019-04-03 21:22 ` [PATCH v6 16/20] x86/clearcpuid: Support multiple clearcpuid options Fenghua Yu
2019-04-03 21:22 ` [PATCH v6 17/20] x86/clearcpuid: Support feature flag string in kernel option clearcpuid Fenghua Yu
2019-04-03 21:22 ` [PATCH v6 18/20] x86/clearcpuid: Apply cleared feature bits that are forced set before Fenghua Yu
2019-04-03 21:22 ` [PATCH v6 19/20] x86/clearcpuid: Clear CPUID bit in CPUID faulting Fenghua Yu
2019-04-03 21:22 ` Fenghua Yu [this message]

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