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ARM: get rid of kmap_high_l1_vipt()

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Since commit 3e4d3af501 "mm: stack based kmap_atomic()", it is no longer
necessary to carry an ad hoc version of kmap_atomic() added in commit
7e5a69e83b "ARM: 6007/1: fix highmem with VIPT cache and DMA" to cope
with reentrancy.

In fact, it is now actively wrong to rely on fixed kmap type indices
(namely KM_L1_CACHE) as kmap_atomic() totally ignores them now and a
concurrent instance of it may reuse any slot for any purpose.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
This commit is contained in:
Nicolas Pitre
2010-12-15 15:14:45 -05:00
committed by Nicolas Pitre
parent b0c3844d8a
commit 39af22a792
4 changed files with 8 additions and 96 deletions
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87
arch/arm/mm/highmem.c
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@@ -140,90 +140,3 @@ struct page *kmap_atomic_to_page(const void *ptr)
pte = TOP_PTE(vaddr);
return pte_page(*pte);
}
#ifdef CONFIG_CPU_CACHE_VIPT
#include <linux/percpu.h>
/*
* The VIVT cache of a highmem page is always flushed before the page
* is unmapped. Hence unmapped highmem pages need no cache maintenance
* in that case.
*
* However unmapped pages may still be cached with a VIPT cache, and
* it is not possible to perform cache maintenance on them using physical
* addresses unfortunately. So we have no choice but to set up a temporary
* virtual mapping for that purpose.
*
* Yet this VIPT cache maintenance may be triggered from DMA support
* functions which are possibly called from interrupt context. As we don't
* want to keep interrupt disabled all the time when such maintenance is
* taking place, we therefore allow for some reentrancy by preserving and
* restoring the previous fixmap entry before the interrupted context is
* resumed. If the reentrancy depth is 0 then there is no need to restore
* the previous fixmap, and leaving the current one in place allow it to
* be reused the next time without a TLB flush (common with DMA).
*/
static DEFINE_PER_CPU(int, kmap_high_l1_vipt_depth);
void *kmap_high_l1_vipt(struct page *page, pte_t *saved_pte)
{
unsigned int idx, cpu;
int *depth;
unsigned long vaddr, flags;
pte_t pte, *ptep;
if (!in_interrupt())
preempt_disable();
cpu = smp_processor_id();
depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
idx = KM_L1_CACHE + KM_TYPE_NR * cpu;
vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
ptep = TOP_PTE(vaddr);
pte = mk_pte(page, kmap_prot);
raw_local_irq_save(flags);
(*depth)++;
if (pte_val(*ptep) == pte_val(pte)) {
*saved_pte = pte;
} else {
*saved_pte = *ptep;
set_pte_ext(ptep, pte, 0);
local_flush_tlb_kernel_page(vaddr);
}
raw_local_irq_restore(flags);
return (void *)vaddr;
}
void kunmap_high_l1_vipt(struct page *page, pte_t saved_pte)
{
unsigned int idx, cpu = smp_processor_id();
int *depth = &per_cpu(kmap_high_l1_vipt_depth, cpu);
unsigned long vaddr, flags;
pte_t pte, *ptep;
idx = KM_L1_CACHE + KM_TYPE_NR * cpu;
vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
ptep = TOP_PTE(vaddr);
pte = mk_pte(page, kmap_prot);
BUG_ON(pte_val(*ptep) != pte_val(pte));
BUG_ON(*depth <= 0);
raw_local_irq_save(flags);
(*depth)--;
if (*depth != 0 && pte_val(pte) != pte_val(saved_pte)) {
set_pte_ext(ptep, saved_pte, 0);
local_flush_tlb_kernel_page(vaddr);
}
raw_local_irq_restore(flags);
if (!in_interrupt())
preempt_enable();
}
#endif /* CONFIG_CPU_CACHE_VIPT */