x86/mm: Enable CR4.PCIDE on supported systems

[pandora-kernel.git] / arch / x86 / kernel / cpu / common.c

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index d0619ad..895e4b8 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -310,6 +310,29 @@ static __cpuinit void setup_smep(struct cpuinfo_x86 *c)
        }
 }
 
+static void setup_pcid(struct cpuinfo_x86 *c)
+{
+       if (cpu_has(c, X86_FEATURE_PCID)) {
+               if (cpu_has(c, X86_FEATURE_PGE) && IS_ENABLED(CONFIG_X86_64)) {
+                       /*
+                        * Regardless of whether PCID is enumerated, the
+                        * SDM says that it can't be enabled in 32-bit mode.
+                        */
+                       set_in_cr4(X86_CR4_PCIDE);
+               } else {
+                       /*
+                        * flush_tlb_all(), as currently implemented, won't
+                        * work if PCID is on but PGE is not.  Since that
+                        * combination doesn't exist on real hardware, there's
+                        * no reason to try to fully support it, but it's
+                        * polite to avoid corrupting data if we're on
+                        * an improperly configured VM.
+                        */
+                       clear_cpu_cap(c, X86_FEATURE_PCID);
+               }
+       }
+}
+
 /*
  * Some CPU features depend on higher CPUID levels, which may not always
  * be available due to CPUID level capping or broken virtualization
@@ -867,6 +890,9 @@ static void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
        /* Disable the PN if appropriate */
        squash_the_stupid_serial_number(c);
 
+       /* Set up PCID */
+       setup_pcid(c);
+
        /*
         * The vendor-specific functions might have changed features.
         * Now we do "generic changes."
@@ -952,11 +978,6 @@ 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();