Commit-ID: 5e8105950a8b3e03e805299b4d05020ee4eda31a Gitweb: https://git.kernel.org/tip/5e8105950a8b3e03e805299b4d05020ee4eda31a Author: Joerg Roedel <[email protected]> AuthorDate: Wed, 18 Jul 2018 11:41:15 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Fri, 20 Jul 2018 01:11:48 +0200
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] --- arch/x86/mm/pti.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) 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: */
