5 files changed, 55 insertions, 60 deletions

diff --git a/arch/x86/kernel/cpu/addon_cpuid_features.c b/arch/x86/kernel/cpu/addon_cpuid_features.c
index 238468ae1993..c2e1ce33c7cb 100644
--- a/arch/x86/kernel/cpu/addon_cpuid_features.c
+++ b/arch/x86/kernel/cpu/addon_cpuid_features.c
@@ -6,6 +6,7 @@
 
 #include <linux/cpu.h>
 
+#include <asm/pat.h>
 #include <asm/processor.h>
 
 struct cpuid_bit {
@@ -48,3 +49,23 @@ void __cpuinit init_scattered_cpuid_features(struct cpuinfo_x86 *c)
                         set_cpu_cap(c, cb->feature);
         }
 }
+
+#ifdef CONFIG_X86_PAT
+void __cpuinit validate_pat_support(struct cpuinfo_x86 *c)
+{
+        switch (c->x86_vendor) {
+        case X86_VENDOR_AMD:
+                if (c->x86 >= 0xf && c->x86 <= 0x11)
+                        return;
+                break;
+        case X86_VENDOR_INTEL:
+                if (c->x86 == 0xF || (c->x86 == 6 && c->x86_model >= 15))
+                        return;
+                break;
+        }
+
+        pat_disable(cpu_has_pat ?
+                    "PAT disabled. Not yet verified on this CPU type." :
+                    "PAT not supported by CPU.");
+}
+#endif
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 35b4f6a9c8ef..d0463a946247 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -12,6 +12,7 @@
 #include <asm/mmu_context.h>
 #include <asm/mtrr.h>
 #include <asm/mce.h>
+#include <asm/pat.h>
 #ifdef CONFIG_X86_LOCAL_APIC
 #include <asm/mpspec.h>
 #include <asm/apic.h>
@@ -308,19 +309,6 @@ static void __cpuinit early_get_cap(struct cpuinfo_x86 *c)
 
         }
 
-        clear_cpu_cap(c, X86_FEATURE_PAT);
-
-        switch (c->x86_vendor) {
-        case X86_VENDOR_AMD:
-                if (c->x86 >= 0xf && c->x86 <= 0x11)
-                        set_cpu_cap(c, X86_FEATURE_PAT);
-                break;
-        case X86_VENDOR_INTEL:
-                if (c->x86 == 0xF || (c->x86 == 6 && c->x86_model >= 15))
-                        set_cpu_cap(c, X86_FEATURE_PAT);
-                break;
-        }
-
 }
 
 /*
@@ -409,18 +397,6 @@ static void __cpuinit generic_identify(struct cpuinfo_x86 *c)
                 init_scattered_cpuid_features(c);
         }
 
-        clear_cpu_cap(c, X86_FEATURE_PAT);
-
-        switch (c->x86_vendor) {
-        case X86_VENDOR_AMD:
-                if (c->x86 >= 0xf && c->x86 <= 0x11)
-                        set_cpu_cap(c, X86_FEATURE_PAT);
-                break;
-        case X86_VENDOR_INTEL:
-                if (c->x86 == 0xF || (c->x86 == 6 && c->x86_model >= 15))
-                        set_cpu_cap(c, X86_FEATURE_PAT);
-                break;
-        }
 }
 
 static void __cpuinit squash_the_stupid_serial_number(struct cpuinfo_x86 *c)
@@ -651,6 +627,7 @@ void __init early_cpu_init(void)
                 cpu_devs[cvdev->vendor] = cvdev->cpu_dev;
 
         early_cpu_detect();
+        validate_pat_support(&boot_cpu_data);
 }
 
 /* Make sure %fs is initialized properly in idle threads */
diff --git a/arch/x86/kernel/setup_64.c b/arch/x86/kernel/setup_64.c
index 22c14e21c97c..80d80fab7006 100644
--- a/arch/x86/kernel/setup_64.c
+++ b/arch/x86/kernel/setup_64.c
@@ -70,6 +70,7 @@
 #include <asm/ds.h>
 #include <asm/topology.h>
 #include <asm/trampoline.h>
+#include <asm/pat.h>
 
 #include <mach_apic.h>
 #ifdef CONFIG_PARAVIRT
@@ -1063,25 +1064,19 @@ static void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c)
         if (c->extended_cpuid_level >= 0x80000007)
                 c->x86_power = cpuid_edx(0x80000007);
 
-
-        clear_cpu_cap(c, X86_FEATURE_PAT);
-
         switch (c->x86_vendor) {
         case X86_VENDOR_AMD:
                 early_init_amd(c);
-                if (c->x86 >= 0xf && c->x86 <= 0x11)
-                        set_cpu_cap(c, X86_FEATURE_PAT);
                 break;
         case X86_VENDOR_INTEL:
                 early_init_intel(c);
-                if (c->x86 == 0xF || (c->x86 == 6 && c->x86_model >= 15))
-                        set_cpu_cap(c, X86_FEATURE_PAT);
                 break;
         case X86_VENDOR_CENTAUR:
                 early_init_centaur(c);
                 break;
         }
 
+        validate_pat_support(c);
 }
 
 /*
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 277446cd30b6..60adbe22efa0 100644
--- 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",
diff --git a/include/asm-x86/pat.h b/include/asm-x86/pat.h
index 8b822b5a1786..88f60cc6a227 100644
--- a/include/asm-x86/pat.h
+++ b/include/asm-x86/pat.h
@@ -4,7 +4,13 @@
 
 #include <linux/types.h>
 
+#ifdef CONFIG_X86_PAT
 extern int pat_wc_enabled;
+extern void validate_pat_support(struct cpuinfo_x86 *c);
+#else
+static const int pat_wc_enabled = 0;
+static inline void validate_pat_support(struct cpuinfo_x86 *c) { }
+#endif
 
 extern void pat_init(void);
 
@@ -12,5 +18,7 @@ extern int reserve_memtype(u64 start, u64 end,
                 unsigned long req_type, unsigned long *ret_type);
 extern int free_memtype(u64 start, u64 end);
 
+extern void pat_disable(char *reason);
+
 #endif