Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
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
Message-Id: <1554326526-172295-21-git-send-email-fenghua.yu@intel.com>
In-Reply-To: <1554326526-172295-1-git-send-email-fenghua.yu@intel.com>
References: <1554326526-172295-1-git-send-email-fenghua.yu@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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