From: Andy Lutomirski <luto@kernel.org>
Date: Tue, 20 Jun 2017 22:22:09 -0700
Subject: x86/mm: Remove reset_lazy_tlbstate()
Git-commit: d54368127a11c6da0776c109a4c65a7b6a815f32
Patch-mainline: v4.13-rc1
References: bsc#1068032 CVE-2017-5754

The only call site also calls idle_task_exit(), and idle_task_exit()
puts us into a clean state by explicitly switching to init_mm.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/3acc7ad02a2ec060d2321a1e0f6de1cb90069517.1498022414.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/include/asm/tlbflush.h |    8 --------
 arch/x86/kernel/smpboot.c       |    1 -
 2 files changed, 9 deletions(-)

--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -313,14 +313,6 @@ void native_flush_tlb_others(const struc
 #define TLBSTATE_OK	1
 #define TLBSTATE_LAZY	2
 
-static inline void reset_lazy_tlbstate(void)
-{
-	this_cpu_write(cpu_tlbstate.state, 0);
-	this_cpu_write(cpu_tlbstate.loaded_mm, &init_mm);
-
-	WARN_ON(read_cr3_pa() != __pa_symbol(swapper_pg_dir));
-}
-
 static inline void arch_tlbbatch_add_mm(struct arch_tlbflush_unmap_batch *batch,
 					struct mm_struct *mm)
 {
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1589,7 +1589,6 @@ void native_cpu_die(unsigned int cpu)
 void play_dead_common(void)
 {
 	idle_task_exit();
-	reset_lazy_tlbstate();
 
 	/* Ack it */
 	(void)cpu_report_death();