x86: PAT: fix ambiguous paranoia check in pat_init()

Starting with commit 8d4a4300854f3971502e81dacd930704cb88f606 (x86:
cleanup PAT cpu validation) the PAT CPU feature flag is not cleared
anymore. Now the error message

  "PAT enabled, but CPU feature cleared"

in pat_init() is misleading.

Furthermore the current code does not check for existence of the PAT
CPU feature flag if a CPU is whitelisted in validate_pat_support.

This patch clears pat_wc_enabled if boot CPU has no PAT feature flag
and adapts the paranoia check.

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 10 insertions, 8 deletions

diff --git a/arch/x86/kernel/cpu/addon_cpuid_features.c b/arch/x86/kernel/cpu/addon_cpuid_features.c
index 0fbd06241e07..2df461f06a52 100644
--- a/arch/x86/kernel/cpu/addon_cpuid_features.c
+++ b/arch/x86/kernel/cpu/addon_cpuid_features.c
@@ -53,6 +53,9 @@ void __cpuinit init_scattered_cpuid_features(struct cpuinfo_x86 *c)
 #ifdef CONFIG_X86_PAT
 void __cpuinit validate_pat_support(struct cpuinfo_x86 *c)
 {
+        if (!cpu_has_pat)
+                pat_disable("PAT not supported by CPU.");
+
         switch (c->x86_vendor) {
         case X86_VENDOR_INTEL:
                 if (c->x86 == 0xF || (c->x86 == 6 && c->x86_model >= 15))
@@ -64,8 +67,6 @@ void __cpuinit validate_pat_support(struct cpuinfo_x86 *c)
                 return;
         }
 
-        pat_disable(cpu_has_pat ?
-                    "PAT disabled. Not yet verified on this CPU type." :
-                    "PAT not supported by CPU.");
+        pat_disable("PAT disabled. Not yet verified on this CPU type.");
 }
 #endif
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 320d644a8107..65105b1195a3 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -76,14 +76,15 @@ void pat_init(void)
                 return;
 
         /* Paranoia check. */
-        if (!cpu_has_pat) {
-                printk(KERN_ERR "PAT enabled, but CPU feature cleared\n");
+        if (!cpu_has_pat && boot_pat_state) {
                 /*
-                 * Panic if this happens on the secondary CPU, and we
+                 * If this happens we are on a secondary CPU, but
                  * switched to PAT on the boot CPU. We have no way to
                  * undo PAT.
-                */
-                BUG_ON(boot_pat_state);
+                 */
+                printk(KERN_ERR "PAT enabled, "
+                       "but not supported by secondary CPU\n");
+                BUG();
         }
 
         /* Set PWT to Write-Combining. All other bits stay the same */