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x86/mm: Add the 'nopcid' boot option to turn off PCID 

The parameter is only present on x86_64 systems to save a few bytes,
as PCID is always disabled on x86_32.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Nadav Amit <nadav.amit@gmail.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/8bbb2e65bcd249a5f18bfb8128b4689f08ac2b60.1498751203.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2017-06-29 08:53:20 -07:00 committed by Ingo Molnar
parent cba4671af7
commit 0790c9aad8
2 changed files with 20 additions and 0 deletions
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2
Documentation/admin-guide/kernel-parameters.txt
View File

@ -2657,6 +2657,8 @@
nopat [X86] Disable PAT (page attribute table extension of
pagetables) support.
nopcid [X86-64] Disable the PCID cpu feature.
norandmaps Don't use address space randomization. Equivalent to
echo 0 > /proc/sys/kernel/randomize_va_space

18
arch/x86/kernel/cpu/common.c
View File

@ -168,6 +168,24 @@ static int __init x86_mpx_setup(char *s)
}
__setup("nompx", x86_mpx_setup);
#ifdef CONFIG_X86_64
static int __init x86_pcid_setup(char *s)
{
/* require an exact match without trailing characters */
if (strlen(s))
return 0;
/* do not emit a message if the feature is not present */
if (!boot_cpu_has(X86_FEATURE_PCID))
return 1;
setup_clear_cpu_cap(X86_FEATURE_PCID);
pr_info("nopcid: PCID feature disabled\n");
return 1;
}
__setup("nopcid", x86_pcid_setup);
#endif
static int __init x86_noinvpcid_setup(char *s)
{
/* noinvpcid doesn't accept parameters */