Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux...

[deliverable/linux.git] / arch / x86 / mm / pat.c

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 277446cd30b6de81a4634061949385cb6eaede69..60adbe22efa0d66e3885cbb39ed5f65c521a8fde 100644 (file)
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -25,31 +25,24 @@
 #include <asm/mtrr.h>
 #include <asm/io.h>
 
-int pat_wc_enabled = 1;
+#ifdef CONFIG_X86_PAT
+int __read_mostly pat_wc_enabled = 1;
 
-static u64 __read_mostly boot_pat_state;
-
-static int nopat(char *str)
+void __init pat_disable(char *reason)
 {
        pat_wc_enabled = 0;
-       printk(KERN_INFO "x86: PAT support disabled.\n");
-
-       return 0;
+       printk(KERN_INFO "%s\n", reason);
 }
-early_param("nopat", nopat);
 
-static int pat_known_cpu(void)
+static int nopat(char *str)
 {
-       if (!pat_wc_enabled)
-               return 0;
-
-       if (cpu_has_pat)
-               return 1;
-
-       pat_wc_enabled = 0;
-       printk(KERN_INFO "CPU and/or kernel does not support PAT.\n");
+       pat_disable("PAT support disabled.");
        return 0;
 }
+early_param("nopat", nopat);
+#endif
+
+static u64 __read_mostly boot_pat_state;
 
 enum {
        PAT_UC = 0,             /* uncached */
@@ -66,17 +59,19 @@ void pat_init(void)
 {
        u64 pat;
 
-#ifndef CONFIG_X86_PAT
-       nopat(NULL);
-#endif
-
-       /* Boot CPU enables PAT based on CPU feature */
-       if (!smp_processor_id() && !pat_known_cpu())
+       if (!pat_wc_enabled)
                return;
 
-       /* APs enable PAT iff boot CPU has enabled it before */
-       if (smp_processor_id() && !pat_wc_enabled)
-               return;
+       /* Paranoia check. */
+       if (!cpu_has_pat) {
+               printk(KERN_ERR "PAT enabled, but CPU feature cleared\n");
+               /*
+                * Panic if this happens on the secondary CPU, and we
+                * switched to PAT on the boot CPU. We have no way to
+                * undo PAT.
+               */
+               BUG_ON(boot_pat_state);
+       }
 
        /* Set PWT to Write-Combining. All other bits stay the same */
        /*
@@ -95,9 +90,8 @@ void pat_init(void)
              PAT(4,WB) | PAT(5,WC) | PAT(6,UC_MINUS) | PAT(7,UC);
 
        /* Boot CPU check */
-       if (!smp_processor_id()) {
+       if (!boot_pat_state)
                rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
-       }
 
        wrmsrl(MSR_IA32_CR_PAT, pat);
        printk(KERN_INFO "x86 PAT enabled: cpu %d, old 0x%Lx, new 0x%Lx\n",