x86/mm: Disable PCID on 32-bit kernels

commit cba4671af7550e008f7a7835f06df0763825bf3e upstream.

32-bit kernels on new hardware will see PCID in CPUID, but PCID can
only be used in 64-bit mode.  Rather than making all PCID code
conditional, just disable the feature on 32-bit builds.

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/2e391769192a4d31b808410c383c6bf0734bc6ea.1498751203.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 46674fb..ad95476 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -159,6 +159,14 @@ static void __init check_config(void)
 
 void __init check_bugs(void)
 {
+#ifdef CONFIG_X86_32
+       /*
+        * Regardless of whether PCID is enumerated, the SDM says
+        * that it can't be enabled in 32-bit mode.
+        */
+       setup_clear_cpu_cap(X86_FEATURE_PCID);
+#endif
+
        identify_boot_cpu();
 #ifndef CONFIG_SMP
        printk(KERN_INFO "CPU: ");

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 1477e70..e7dd20a 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -934,6 +934,11 @@ void __cpuinit identify_secondary_cpu(struct cpuinfo_x86 *c)
        BUG_ON(c == &boot_cpu_data);
        identify_cpu(c);
 #ifdef CONFIG_X86_32
+       /*
+        * Regardless of whether PCID is enumerated, the SDM says
+        * that it can't be enabled in 32-bit mode.
+        */
+       clear_cpu_cap(c, X86_FEATURE_PCID);
        enable_sep_cpu();
 #endif
        mtrr_ap_init();