From: Joerg Roedel <jroedel@xxxxxxx>
Warn the user in case the performance can be significantly
improved by switching to a 64-bit kernel.
Suggested-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
---
arch/x86/mm/pti.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index e3059bb0..0ab41fb 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -497,6 +497,22 @@ void __init pti_init(void)
pr_info("enabled\n");
+#ifdef CONFIG_X86_32
+ if (boot_cpu_has(X86_FEATURE_PCID)) {
+ /* Use printk to work around pr_fmt() */
+ printk(KERN_WARNING "\n");
+ printk(KERN_WARNING "************************************************************\n");
+ printk(KERN_WARNING "** WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! **\n");
+ printk(KERN_WARNING "** **\n");
+ printk(KERN_WARNING "** You are using 32-bit PTI on a 64-bit PCID-capable CPU. **\n");
+ printk(KERN_WARNING "** Your performance will increase dramatically if you **\n");
+ printk(KERN_WARNING "** switch to a 64-bit kernel! **\n");
+ printk(KERN_WARNING "** **\n");
+ printk(KERN_WARNING "** WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! **\n");
+ printk(KERN_WARNING "************************************************************\n");
+ }
+#endif
+
pti_clone_user_shared();
/* Undo all global bits from the init pagetables in head_64.S: */
--
2.7.4
