x86/pti: Fix boot problems from Global-bit setting

commit 16dce603adc9de4237b7bf2ff5c5290f34373e7b

Part of the global bit _setting_ patches also includes clearing the
Global bit when it should not be enabled.  That is done with
set_memory_nonglobal(), which uses change_page_attr_clear() in
pageattr.c under the covers.

The TLB flushing code inside pageattr.c has has checks like
BUG_ON(irqs_disabled()), looking for interrupt disabling that might
cause deadlocks.  But, these also trip in early boot on certain
preempt configurations.  Just copy the existing BUG_ON() sequence from
cpa_flush_range() to the other two sites and check for early boot.

Fixes: 39114b7a (x86/pti: Never implicitly clear _PAGE_GLOBAL for kernel image)
Reported-by: NMariusz Ceier <mceier@gmail.com>
Reported-by: NAaro Koskinen <aaro.koskinen@nokia.com>
Signed-off-by: NDave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Tested-by: NAaro Koskinen <aaro.koskinen@nokia.com>
Acked-by: NIngo Molnar <mingo@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Kees Cook <keescook@google.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Link: https://lkml.kernel.org/r/20180420222019.20C4A410@viggo.jf.intel.com

arch/x86/mm/pageattr.c

@@ -172,7 +172,7 @@ static void __cpa_flush_all(void *arg)
 
 static void cpa_flush_all(unsigned long cache)
 {
-	BUG_ON(irqs_disabled());
+	BUG_ON(irqs_disabled() && !early_boot_irqs_disabled);
 
 	on_each_cpu(__cpa_flush_all, (void *) cache, 1);
 }
@@ -236,7 +236,7 @@ static void cpa_flush_array(unsigned long *start, int numpages, int cache,
 	unsigned long do_wbinvd = cache && numpages >= 1024; /* 4M threshold */
 #endif
 
-	BUG_ON(irqs_disabled());
+	BUG_ON(irqs_disabled() && !early_boot_irqs_disabled);
 
 	on_each_cpu(__cpa_flush_all, (void *) do_wbinvd, 1);