Patch "x86/mm: Fix INVPCID asm constraint" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    x86/mm: Fix INVPCID asm constraint

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-mm-fix-invpcid-asm-constraint.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From e2c7698cd61f11d4077fdb28148b2d31b82ac848 Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bp@suse.de>
Date: Wed, 10 Feb 2016 15:51:16 +0100
Subject: x86/mm: Fix INVPCID asm constraint
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From: Borislav Petkov <bp@suse.de>

commit e2c7698cd61f11d4077fdb28148b2d31b82ac848 upstream.

So we want to specify the dependency on both @pcid and @addr so that the
compiler doesn't reorder accesses to them *before* the TLB flush. But
for that to work, we need to express this properly in the inline asm and
deref the whole desc array, not the pointer to it. See clwb() for an
example.

This fixes the build error on 32-bit:

  arch/x86/include/asm/tlbflush.h: In function ‘__invpcid’:
  arch/x86/include/asm/tlbflush.h:26:18: error: memory input 0 is not directly addressable

which gcc4.7 caught but 5.x didn't. Which is strange. :-\

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Michael Matz <matz@suse.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/include/asm/tlbflush.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -10,7 +10,7 @@
 static inline void __invpcid(unsigned long pcid, unsigned long addr,
 			     unsigned long type)
 {
-	u64 desc[2] = { pcid, addr };
+	struct { u64 d[2]; } desc = { { pcid, addr } };
 
 	/*
 	 * The memory clobber is because the whole point is to invalidate
@@ -22,7 +22,7 @@ static inline void __invpcid(unsigned lo
 	 * invpcid (%rcx), %rax in long mode.
 	 */
 	asm volatile (".byte 0x66, 0x0f, 0x38, 0x82, 0x01"
-		      : : "m" (desc), "a" (type), "c" (desc) : "memory");
+		      : : "m" (desc), "a" (type), "c" (&desc) : "memory");
 }
 
 #define INVPCID_TYPE_INDIV_ADDR		0


Patches currently in stable-queue which might be from bp@suse.de are

queue-4.4/x86-mm-sched-core-uninline-switch_mm.patch
queue-4.4/x86-mm-add-a-noinvpcid-boot-option-to-turn-off-invpcid.patch
queue-4.4/x86-mm-if-invpcid-is-available-use-it-to-flush-global-mappings.patch
queue-4.4/x86-mm-add-invpcid-helpers.patch
queue-4.4/sched-core-add-switch_mm_irqs_off-and-use-it-in-the-scheduler.patch
queue-4.4/arm-hide-finish_arch_post_lock_switch-from-modules.patch
queue-4.4/x86-mm-sched-core-turn-off-irqs-in-switch_mm.patch
queue-4.4/x86-mm-fix-invpcid-asm-constraint.patch
queue-4.4/x86-mm-build-arch-x86-mm-tlb.c-even-on-smp.patch
queue-4.4/sched-core-idle_task_exit-shouldn-t-use-switch_mm_irqs_off.patch