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authorJoerg Roedel <jroedel@suse.de>2018-07-18 11:41:15 +0200
committerThomas Gleixner <tglx@linutronix.de>2018-07-20 01:11:48 +0200
commit5e8105950a8b3e03e805299b4d05020ee4eda31a (patch)
treee5ab66cb17129a284934830bf40eda4b7ebfcff8 /arch/x86/mm
parent7757d607c6b31867777de42e1fb0210b9c5d8b70 (diff)
download96b-common-5e8105950a8b3e03e805299b4d05020ee4eda31a.tar.gz
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 <luto@kernel.org> Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Pavel Machek <pavel@ucw.cz> Cc: "H . Peter Anvin" <hpa@zytor.com> Cc: linux-mm@kvack.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Brian Gerst <brgerst@gmail.com> Cc: David Laight <David.Laight@aculab.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Eduardo Valentin <eduval@amazon.com> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Will Deacon <will.deacon@arm.com> Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Waiman Long <llong@redhat.com> Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca> Cc: joro@8bytes.org Link: https://lkml.kernel.org/r/1531906876-13451-39-git-send-email-joro@8bytes.org
Diffstat (limited to 'arch/x86/mm')
-rw-r--r--arch/x86/mm/pti.c22
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: */