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@xxxxxxxxx> --- .../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
