diff options
| author | Joerg Roedel <[email protected]> | 2018-07-18 11:41:15 +0200 |
|---|---|---|
| committer | Thomas Gleixner <[email protected]> | 2018-07-20 01:11:48 +0200 |
| commit | 5e8105950a8b3e03e805299b4d05020ee4eda31a (patch) | |
| tree | e5ab66cb17129a284934830bf40eda4b7ebfcff8 | |
| parent | 7757d607c6b31867777de42e1fb0210b9c5d8b70 (diff) | |
x86/mm/pti: Add Warning when booting on a PCID capable CPU
Warn the user in case the performance can be significantly improved by
switching to a 64-bit kernel.
Suggested-by: Andy Lutomirski <[email protected]>
Signed-off-by: Joerg Roedel <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Pavel Machek <[email protected]>
Cc: "H . Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: Linus Torvalds <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Jiri Kosina <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: David Laight <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Eduardo Valentin <[email protected]>
Cc: Greg KH <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Andrea Arcangeli <[email protected]>
Cc: Waiman Long <[email protected]>
Cc: "David H . Gutteridge" <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
| -rw-r--r-- | arch/x86/mm/pti.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index a536ecc91847..7b1c85759005 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -517,6 +517,28 @@ void __init pti_init(void) pr_info("enabled\n"); +#ifdef CONFIG_X86_32 + /* + * We check for X86_FEATURE_PCID here. But the init-code will + * clear the feature flag on 32 bit because the feature is not + * supported on 32 bit anyway. To print the warning we need to + * check with cpuid directly again. + */ + if (cpuid_ecx(0x1) && BIT(17)) { + /* 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: */ |