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Subject[PATCH 4.14 110/165] mm/tlb, x86/mm: Support invalidating TLB caches for RCU_TABLE_FREE
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <peterz@infradead.org>

commit d86564a2f085b79ec046a5cba90188e612352806 upstream.

Jann reported that x86 was missing required TLB invalidates when he
hit the !*batch slow path in tlb_remove_table().

This is indeed the case; RCU_TABLE_FREE does not provide TLB (cache)
invalidates, the PowerPC-hash where this code originated and the
Sparc-hash where this was subsequently used did not need that. ARM
which later used this put an explicit TLB invalidate in their
__p*_free_tlb() functions, and PowerPC-radix followed that example.

But when we hooked up x86 we failed to consider this. Fix this by
(optionally) hooking tlb_remove_table() into the TLB invalidate code.

NOTE: s390 was also needing something like this and might now
be able to use the generic code again.

[ Modified to be on top of Nick's cleanups, which simplified this patch
now that tlb_flush_mmu_tlbonly() really only flushes the TLB - Linus ]

Fixes: 9e52fc2b50de ("x86/mm: Enable RCU based page table freeing (CONFIG_HAVE_RCU_TABLE_FREE=y)")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rik van Riel <riel@surriel.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: David Miller <davem@davemloft.net>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/Kconfig | 3 +++
arch/x86/Kconfig | 1 +
mm/memory.c | 18 ++++++++++++++++++
3 files changed, 22 insertions(+)

--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -336,6 +336,9 @@ config HAVE_ARCH_JUMP_LABEL
config HAVE_RCU_TABLE_FREE
bool

+config HAVE_RCU_TABLE_INVALIDATE
+ bool
+
config ARCH_HAVE_NMI_SAFE_CMPXCHG
bool

--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -170,6 +170,7 @@ config X86
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
select HAVE_RCU_TABLE_FREE
+ select HAVE_RCU_TABLE_INVALIDATE if HAVE_RCU_TABLE_FREE
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_RELIABLE_STACKTRACE if X86_64 && UNWINDER_FRAME_POINTER && STACK_VALIDATION
select HAVE_STACK_VALIDATION if X86_64
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -331,6 +331,21 @@ bool __tlb_remove_page_size(struct mmu_g
* See the comment near struct mmu_table_batch.
*/

+/*
+ * If we want tlb_remove_table() to imply TLB invalidates.
+ */
+static inline void tlb_table_invalidate(struct mmu_gather *tlb)
+{
+#ifdef CONFIG_HAVE_RCU_TABLE_INVALIDATE
+ /*
+ * Invalidate page-table caches used by hardware walkers. Then we still
+ * need to RCU-sched wait while freeing the pages because software
+ * walkers can still be in-flight.
+ */
+ tlb_flush_mmu_tlbonly(tlb);
+#endif
+}
+
static void tlb_remove_table_smp_sync(void *arg)
{
/* Simply deliver the interrupt */
@@ -367,6 +382,7 @@ void tlb_table_flush(struct mmu_gather *
struct mmu_table_batch **batch = &tlb->batch;

if (*batch) {
+ tlb_table_invalidate(tlb);
call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
*batch = NULL;
}
@@ -388,11 +404,13 @@ void tlb_remove_table(struct mmu_gather
if (*batch == NULL) {
*batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
if (*batch == NULL) {
+ tlb_table_invalidate(tlb);
tlb_remove_table_one(table);
return;
}
(*batch)->nr = 0;
}
+
(*batch)->tables[(*batch)->nr++] = table;
if ((*batch)->nr == MAX_TABLE_BATCH)
tlb_table_flush(tlb);

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