[PATCH 1/5] x86, pti: fix boot problems from Global-bit setting

From: Dave Hansen
Date: Fri Apr 20 2018 - 18:24:18 EST

From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>

Part of the global bit _setting_ patches also includes clearing the
Global bit when we do not want it. 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.

Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Fixes: 39114b7a7 (x86/pti: Never implicitly clear _PAGE_GLOBAL for kernel image)
Reported-by: Mariusz Ceier <mceier@xxxxxxxxx>
Reported-by: Aaro Koskinen <aaro.koskinen@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Nadav Amit <namit@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx

b/arch/x86/mm/pageattr.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN arch/x86/mm/pageattr.c~pti-glb-boot-problem-fix arch/x86/mm/pageattr.c
--- a/arch/x86/mm/pageattr.c~pti-glb-boot-problem-fix 2018-04-20 14:10:01.086749169 -0700
+++ b/arch/x86/mm/pageattr.c 2018-04-20 14:10:01.090749169 -0700
@@ -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 lon
unsigned long do_wbinvd = cache && numpages >= 1024; /* 4M threshold */

- BUG_ON(irqs_disabled());
+ BUG_ON(irqs_disabled() && !early_boot_irqs_disabled);

on_each_cpu(__cpa_flush_all, (void *) do_wbinvd, 1);