mm/tlb, x86/mm: Support invalidating TLB caches for RCU_TABLE_FREE

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>

diff --git a/arch/Kconfig b/arch/Kconfig
index 4426e96..b82f21f 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -362,6 +362,9 @@ config HAVE_ARCH_JUMP_LABEL
 config HAVE_RCU_TABLE_FREE
        bool
 
+config HAVE_RCU_TABLE_INVALIDATE
+       bool
+
 config ARCH_HAVE_NMI_SAFE_CMPXCHG
        bool
 

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 512003f..b9d3781 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -181,6 +181,7 @@ 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 || UNWINDER_ORC) && STACK_VALIDATION
        select HAVE_STACKPROTECTOR              if CC_HAS_SANE_STACKPROTECTOR

diff --git a/mm/memory.c b/mm/memory.c
index 1893751..8b34429 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -330,6 +330,21 @@ bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, int page_
  * 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 */
@@ -366,6 +381,7 @@ void tlb_table_flush(struct mmu_gather *tlb)
        struct mmu_table_batch **batch = &tlb->batch;
 
        if (*batch) {
+               tlb_table_invalidate(tlb);
                call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
                *batch = NULL;
        }
@@ -378,11 +394,13 @@ void tlb_remove_table(struct mmu_gather *tlb, void *table)
        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);