[PATCH 4.1 19/65] x86/mm: Add the 'nopcid' boot option to turn off PCID
From: Pavel Tatashin
Date: Mon Mar 05 2018 - 19:38:27 EST
From: Andy Lutomirski <luto@xxxxxxxxxx>
commit 0790c9aad84901ca1bdc14746175549c8b5da215 upstream.
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@xxxxxxxxxx>
Reviewed-by: Nadav Amit <nadav.amit@xxxxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Link: http://lkml.kernel.org/r/8bbb2e65bcd249a5f18bfb8128b4689f08ac2b60.1498751203.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
(cherry picked from commit dcccd3c266e24ce80ecf592765315c54c222ac33)
Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
---
Documentation/kernel-parameters.txt | 2 ++
arch/x86/kernel/cpu/common.c | 18 ++++++++++++++++++
2 files changed, 20 insertions(+)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index ceaab09a279e..97bc24101896 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2471,6 +2471,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
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
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 90ef802d9d90..843be1de5ddb 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -172,6 +172,24 @@ static int __init x86_xsaves_setup(char *s)
}
__setup("noxsaves", x86_xsaves_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 */
--
2.16.2