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>

1 files changed, 6 insertions, 5 deletions

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 */