| From: Andy Lutomirski <luto@kernel.org> |
| Date: Thu, 29 Jun 2017 08:53:20 -0700 |
| Subject: x86/mm: Add the 'nopcid' boot option to turn off PCID |
| |
| 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@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> |
| [Hugh Dickins: Backported to 3.2: |
| - Documentation/admin-guide/kernel-parameters.txt (not in this tree) |
| - Documentation/kernel-parameters.txt (patched instead of that)] |
| Signed-off-by: Hugh Dickins <hughd@google.com> |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| 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 b71a8ea90180..4f43fd315ecd 100644 |
| --- a/Documentation/kernel-parameters.txt |
| +++ b/Documentation/kernel-parameters.txt |
| @@ -1829,6 +1829,8 @@ 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 e7dd20a3c498..d0619ade395b 100644 |
| --- a/arch/x86/kernel/cpu/common.c |
| +++ b/arch/x86/kernel/cpu/common.c |
| @@ -155,6 +155,24 @@ static int __init x86_xsaveopt_setup(char *s) |
| } |
| __setup("noxsaveopt", x86_xsaveopt_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 */ |
| |