2 files changed, 27 insertions, 12 deletions

diff --git a/arch/arm/include/asm/highmem.h b/arch/arm/include/asm/highmem.h
index 7080e2c8fa62..a4edd19dd3d6 100644
--- a/arch/arm/include/asm/highmem.h
+++ b/arch/arm/include/asm/highmem.h
@@ -19,11 +19,36 @@
 
 extern pte_t *pkmap_page_table;
 
+extern void *kmap_high(struct page *page);
+extern void kunmap_high(struct page *page);
+
+/*
+ * The reason for kmap_high_get() is to ensure that the currently kmap'd
+ * page usage count does not decrease to zero while we're using its
+ * existing virtual mapping in an atomic context.  With a VIVT cache this
+ * is essential to do, but with a VIPT cache this is only an optimization
+ * so not to pay the price of establishing a second mapping if an existing
+ * one can be used.  However, on platforms without hardware TLB maintenance
+ * broadcast, we simply cannot use ARCH_NEEDS_KMAP_HIGH_GET at all since
+ * the locking involved must also disable IRQs which is incompatible with
+ * the IPI mechanism used by global TLB operations.
+ */
 #define ARCH_NEEDS_KMAP_HIGH_GET
+#if defined(CONFIG_SMP) && defined(CONFIG_CPU_TLB_V6)
+#undef ARCH_NEEDS_KMAP_HIGH_GET
+#if defined(CONFIG_HIGHMEM) && defined(CONFIG_CPU_CACHE_VIVT)
+#error "The sum of features in your kernel config cannot be supported together"
+#endif
+#endif
 
-extern void *kmap_high(struct page *page);
+#ifdef ARCH_NEEDS_KMAP_HIGH_GET
 extern void *kmap_high_get(struct page *page);
-extern void kunmap_high(struct page *page);
+#else
+static inline void *kmap_high_get(struct page *page)
+{
+        return NULL;
+}
+#endif
 
 /*
  * The following functions are already defined by <linux/highmem.h>
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 3c67e92f7d59..ff7b43b5885a 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -827,16 +827,6 @@ static void __init sanity_check_meminfo(void)
                          * rather difficult.
                          */
                         reason = "with VIPT aliasing cache";
-                } else if (is_smp() && tlb_ops_need_broadcast()) {
-                        /*
-                         * kmap_high needs to occasionally flush TLB entries,
-                         * however, if the TLB entries need to be broadcast
-                         * we may deadlock:
-                         *  kmap_high(irqs off)->flush_all_zero_pkmaps->
-                         *  flush_tlb_kernel_range->smp_call_function_many
-                         *   (must not be called with irqs off)
-                         */
-                        reason = "without hardware TLB ops broadcasting";
                 }
                 if (reason) {
                         printk(KERN_CRIT "HIGHMEM is not supported %s, ignoring high memory\n",