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Subject[PATCH v7 21/21] x86/clearcpuid: Change document for kernel option clearcpuid
Date
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
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