From: Andy Lutomirski <luto@kernel.org>

Share the FIX_USR_SHARED PMDs so the user space and kernel space page
tables have the same PMD page.

[ tglx: Made it use the FIX_USR_SHARED range so later additions
	are covered automatically ]

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.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: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.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
---
 arch/x86/mm/pti.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -233,6 +233,23 @@ pti_clone_pmds(unsigned long start, unsi
 }
 
 /*
+ * Clone the populated PMDs of the user shared fixmaps into the user space
+ * visible page table.
+ */
+static void __init pti_clone_user_shared(void)
+{
+	unsigned long bot, top;
+
+	bot = __fix_to_virt(FIX_USR_SHARED_BOTTOM);
+	top = __fix_to_virt(FIX_USR_SHARED_TOP) + PAGE_SIZE;
+
+	/* Top of the user shared block must be PMD-aligned. */
+	WARN_ON(top & ~PMD_MASK);
+
+	pti_clone_pmds(bot, top, 0);
+}
+
+/*
  * Initialize kernel page table isolation
  */
 void __init pti_init(void)
@@ -241,4 +258,6 @@ void __init pti_init(void)
 		return;
 
 	pr_info("enabled\n");
+
+	pti_clone_user_shared();
 }