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authorNicolas Pitre <nico@fluxnic.net>2011-01-25 21:35:38 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2011-02-23 17:24:17 +0000
commitaaa50048f6ce44af66ce0389d4cc6a8348333271 (patch)
treea41e04a190420fb970981b8535db7cc9f6e583bd /arch/arm/mm/mmu.c
parentc191789c787f488fdb74de0ee55258f71a427704 (diff)
ARM: 6639/1: allow highmem on SMP platforms without h/w TLB ops broadcast
In commit e616c591405c168f6dc3dfd1221e105adfe49b8d, highmem support was deactivated for SMP platforms without hardware TLB ops broadcast because usage of kmap_high_get() requires that IRQs be disabled when kmap_lock is locked which is incompatible with the IPI mechanism used by the software TLB ops broadcast invoked through flush_all_zero_pkmaps(). 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 due to cache coherency issues, 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 VIPT platforms without hardware TLB maintenance we can give up on that optimization in order to be able to use highmem. From ARMv7 onwards the TLB ops are broadcasted in hardware, so let's disable ARCH_NEEDS_KMAP_HIGH_GET only when CONFIG_SMP and CONFIG_CPU_TLB_V6 are defined. Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org> Tested-by: Saeed Bishara <saeed.bishara@gmail.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/mm/mmu.c')
-rw-r--r--arch/arm/mm/mmu.c10
1 files changed, 0 insertions, 10 deletions
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 3c67e92f7d5..ff7b43b5885 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",