Patch "x86/mm: Give each mm TLB flush generation a unique ID" has been added to the 4.9-stable tree

From f39681ed0f48498b80455095376f11535feea332 Mon Sep 17 00:00:00 2001

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

x86/mm: Give each mm TLB flush generation a unique ID

to the 4.9-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-give-each-mm-tlb-flush-generation-a-unique-id.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From f39681ed0f48498b80455095376f11535feea332 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <[email protected]>
Date: Thu, 29 Jun 2017 08:53:15 -0700
Subject: x86/mm: Give each mm TLB flush generation a unique ID

From: Andy Lutomirski <[email protected]>

commit f39681ed0f48498b80455095376f11535feea332 upstream.

This adds two new variables to mmu_context_t: ctx_id and tlb_gen. ctx_id uniquely identifies the mm_struct and will never be reused. For a given mm_struct (and hence ctx_id), tlb_gen is a monotonic

count of the number of times that a TLB flush has been requested. The pair (ctx_id, tlb_gen) can be used as an identifier for TLB flush actions and will be used in subsequent patches to reliably determine whether all needed TLB flushes have occurred on a given CPU.

This patch is split out for ease of review. By itself, it has no real effect other than creating and updating the new variables.

Signed-off-by Andy Lutomirski <[email protected]>

Reviewed-by Nadav Amit <[email protected]>

Reviewed-by Thomas Gleixner <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Arjan van de Ven <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Dave Hansen <[email protected]>

Cc Linus Torvalds <[email protected]>

Cc Mel Gorman <[email protected]>

Cc Peter Zijlstra <[email protected]>

Cc Rik van Riel <[email protected]>

Cc [email protected]

Link http://lkml.kernel.org/r/413a91c24dab3ed0caa5f4e4d017d87b0857f920.1498751203.git.luto@kernel.org open here

Signed-off-by Ingo Molnar <[email protected]>

Signed-off-by Tim Chen <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 arch/x86/include/asm/mmu.h         |   15 +++++++++++++--
 arch/x86/include/asm/mmu_context.h |    5 +++++
 arch/x86/mm/tlb.c                  |    2 ++
 3 files changed, 20 insertions(+), 2 deletions(-)

arch/x86/include/asm/mmu.h +13 -2

@@ -3,12 +3,18 @@
 
 #include <linux/spinlock.h>
 #include <linux/mutex.h>
+#include <linux/atomic.h>
 
 /*
- * The x86 doesn't have a mmu context, but
- * we put the segment information here.
+ * x86 has arch-specific MMU state beyond what lives in mm_struct.
  */
 typedef struct {
+	/*
+	 * ctx_id uniquely identifies this mm_struct.  A ctx_id will never
+	 * be reused, and zero is not a valid ctx_id.
+	 */
+	u64 ctx_id;
+
 #ifdef CONFIG_MODIFY_LDT_SYSCALL
 	struct ldt_struct *ldt;
 #endif

@@ -33,6 +39,11 @@ typedef struct {
 #endif
 } mm_context_t;
 
+#define INIT_MM_CONTEXT(mm)						\
+	.context = {							\
+		.ctx_id = 1,						\
+	}
+
 void leave_mm(int cpu);
 
 #endif /* _ASM_X86_MMU_H */

arch/x86/include/asm/mmu_context.h +5 -0

@@ -12,6 +12,9 @@
 #include <asm/tlbflush.h>
 #include <asm/paravirt.h>
 #include <asm/mpx.h>
+
+extern atomic64_t last_mm_ctx_id;
+
 #ifndef CONFIG_PARAVIRT
 static inline void paravirt_activate_mm(struct mm_struct *prev,
 					struct mm_struct *next)

@@ -106,6 +109,8 @@ static inline void enter_lazy_tlb(struct
 static inline int init_new_context(struct task_struct *tsk,
 				   struct mm_struct *mm)
 {
+	mm->context.ctx_id = atomic64_inc_return(&last_mm_ctx_id);
+
 	#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
 	if (cpu_feature_enabled(X86_FEATURE_OSPKE)) {
 		/* pkey 0 is the default and always allocated */

arch/x86/mm/tlb.c +2 -0

@@ -29,6 +29,8 @@
  *	Implement flush IPI by CALL_FUNCTION_VECTOR, Alex Shi
  */
 
+atomic64_t last_mm_ctx_id = ATOMIC64_INIT(1);
+
 struct flush_tlb_info {
 	struct mm_struct *flush_mm;
 	unsigned long flush_start;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/nospec-allow-index-argument-to-have-const-qualified-type.patch queue-4.9/x86-speculation-use-indirect-branch-prediction-barrier-in-context-switch.patch queue-4.9/x86-mm-give-each-mm-tlb-flush-generation-a-unique-id.patch

Quoted 21 lines · On 03/07/2018 09:37 AM, [email protected] wrote:

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

x86/mm: Give each mm TLB flush generation a unique ID

to the 4.9-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-give-each-mm-tlb-flush-generation-a-unique-id.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From f39681ed0f48498b80455095376f11535feea332 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <[email protected]>
Date: Thu, 29 Jun 2017 08:53:15 -0700
Subject: x86/mm: Give each mm TLB flush generation a unique ID

Quoted 7 lines

From: Andy Lutomirski <[email protected]>

commit f39681ed0f48498b80455095376f11535feea332 upstream.

This adds two new variables to mmu_context_t: ctx_id and tlb_gen. ctx_id uniquely identifies the mm_struct and will never be reused. For a given mm_struct (and hence ctx_id), tlb_gen is a monotonic

Greg, I've only pulled the unique ctx_id part of the original patch and not the tlb_gen changes. The unique ctx_id is a very simple change
without needing other related changes that tlb_gen will require.

You may want to update the comment to reflect this.