3 files changed, 50 insertions, 10 deletions

diff --git a/arch/arm/include/asm/smp_plat.h b/arch/arm/include/asm/smp_plat.h
new file mode 100644
index 000000000000..59303e200845
--- /dev/null
+++ b/arch/arm/include/asm/smp_plat.h
@@ -0,0 +1,16 @@
+/*
+ * ARM specific SMP header, this contains our implementation
+ * details.
+ */
+#ifndef __ASMARM_SMP_PLAT_H
+#define __ASMARM_SMP_PLAT_H
+
+#include <asm/cputype.h>
+
+/* all SMP configurations have the extended CPUID registers */
+static inline int tlb_ops_need_broadcast(void)
+{
+        return ((read_cpuid_ext(CPUID_EXT_MMFR3) >> 12) & 0xf) < 2;
+}
+
+#endif
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index e0d32770bb3d..9d015ee5747a 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -36,6 +36,7 @@
 #include <asm/tlbflush.h>
 #include <asm/ptrace.h>
 #include <asm/localtimer.h>
+#include <asm/smp_plat.h>
 
 /*
  * as from 2.5, kernels no longer have an init_tasks structure
@@ -586,12 +587,6 @@ struct tlb_args {
         unsigned long ta_end;
 };
 
-/* all SMP configurations have the extended CPUID registers */
-static inline int tlb_ops_need_broadcast(void)
-{
-        return ((read_cpuid_ext(CPUID_EXT_MMFR3) >> 12) & 0xf) < 2;
-}
-
 static inline void ipi_flush_tlb_all(void *ignored)
 {
         local_flush_tlb_all();
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index ce551ec2cb23..02243eeccf50 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -21,6 +21,7 @@
 #include <asm/cachetype.h>
 #include <asm/setup.h>
 #include <asm/sizes.h>
+#include <asm/smp_plat.h>
 #include <asm/tlb.h>
 #include <asm/highmem.h>
 
@@ -709,10 +710,6 @@ static void __init sanity_check_meminfo(void)
                         if (meminfo.nr_banks >= NR_BANKS) {
                                 printk(KERN_CRIT "NR_BANKS too low, "
                                                  "ignoring high memory\n");
-                        } else if (cache_is_vipt_aliasing()) {
-                                printk(KERN_CRIT "HIGHMEM is not yet supported "
-                                                 "with VIPT aliasing cache, "
-                                                 "ignoring high memory\n");
                         } else {
                                 memmove(bank + 1, bank,
                                         (meminfo.nr_banks - i) * sizeof(*bank));
@@ -756,6 +753,38 @@ static void __init sanity_check_meminfo(void)
 #endif
                 j++;
         }
+#ifdef CONFIG_HIGHMEM
+        if (highmem) {
+                const char *reason = NULL;
+
+                if (cache_is_vipt_aliasing()) {
+                        /*
+                         * Interactions between kmap and other mappings
+                         * make highmem support with aliasing VIPT caches
+                         * rather difficult.
+                         */
+                        reason = "with VIPT aliasing cache";
+#ifdef CONFIG_SMP
+                } else if (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";
+#endif
+                }
+                if (reason) {
+                        printk(KERN_CRIT "HIGHMEM is not supported %s, ignoring high memory\n",
+                                reason);
+                        while (j > 0 && meminfo.bank[j - 1].highmem)
+                                j--;
+                }
+        }
+#endif
         meminfo.nr_banks = j;
 }