From aaa50048f6ce44af66ce0389d4cc6a8348333271 Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Tue, 25 Jan 2011 21:35:38 +0100 Subject: 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 Tested-by: Saeed Bishara Signed-off-by: Russell King --- arch/arm/mm/mmu.c | 10 ---------- 1 file changed, 10 deletions(-) (limited to 'arch/arm/mm') 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", -- cgit v1.2.3-70-g09d2