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Commit 10ce13bb authored by Laura Abbott's avatar Laura Abbott Committed by Vijayanand Jitta
Browse files

arm: highmem: Add support for flushing kmap_atomic mappings 



The highmem code provides kmap_flush_unused to ensure all kmap
mappings are really removed if they are unused. This code does not
handle kmap_atomic mappings since they are managed separately.
This prevents an issue for any code which relies on having absolutely
no mappings for a particular page. Rather than pay the penalty of
having CONFIG_DEBUG_HIGHMEM on all the time, add functionality
to remove the kmap_atomic mappings in a similar way to kmap_flush_unused.

Change-Id: I9d73abad693c18f2daa1647353e7592b255475b0
Signed-off-by: default avatarLaura Abbott <lauraa@codeaurora.org>
parent 98055d18

arch/arm/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -230,6 +230,9 @@ config NEED_RET_TO_USER 
config ARCH_MTD_XIP

	bool



config ARCH_WANT_KMAP_ATOMIC_FLUSH

	bool



config VECTORS_BASE

	hex

	default 0xffff0000 if MMU || CPU_HIGH_VECTOR
@@ -567,6 +570,7 @@ config ARCH_QCOM 
       select SPARSE_IRQ

       select USE_OF

       select PINCTRL

       select ARCH_WANT_KMAP_ATOMIC_FLUSH

       help

         Support for Qualcomm MSM/QSD based systems.  This runs on the

         apps processor of the MSM/QSD and depends on a shared memory

arch/arm/mm/highmem.c

+56 −0
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
 * published by the Free Software Foundation.

 */



#include <linux/cpu.h>

#include <linux/module.h>

#include <linux/highmem.h>

#include <linux/interrupt.h>
@@ -147,3 +148,58 @@ void *kmap_atomic_pfn(unsigned long pfn) 


	return (void *)vaddr;

}



#ifdef CONFIG_ARCH_WANT_KMAP_ATOMIC_FLUSH

static void kmap_remove_unused_cpu(int cpu)

{

	int start_idx, idx, type;



	pagefault_disable();

	type = kmap_atomic_idx();

	start_idx = type + 1 + KM_TYPE_NR * cpu;



	for (idx = start_idx; idx < KM_TYPE_NR + KM_TYPE_NR * cpu; idx++) {

		unsigned long vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);

		pte_t ptep;



		ptep = get_top_pte(vaddr);

		if (ptep)

			set_top_pte(vaddr, __pte(0));

	}

	pagefault_enable();

}



static void kmap_remove_unused(void *unused)

{

	kmap_remove_unused_cpu(smp_processor_id());

}



void kmap_atomic_flush_unused(void)

{

	on_each_cpu(kmap_remove_unused, NULL, 1);

}



static int hotplug_kmap_atomic_callback(struct notifier_block *nfb,

					unsigned long action, void *hcpu)

{

	switch (action & (~CPU_TASKS_FROZEN)) {

	case CPU_DYING:

		kmap_remove_unused_cpu((int)hcpu);

		break;

	default:

		break;

	}



	return NOTIFY_OK;

}



static struct notifier_block hotplug_kmap_atomic_notifier = {

	.notifier_call = hotplug_kmap_atomic_callback,

};



static int __init init_kmap_atomic(void)

{

	return register_hotcpu_notifier(&hotplug_kmap_atomic_notifier);

}

early_initcall(init_kmap_atomic);

#endif