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140 lines
4.0 KiB
140 lines
4.0 KiB
/* |
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* Copyright (C) 2015 Synopsys, Inc. (www.synopsys.com) |
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* |
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* This program is free software; you can redistribute it and/or modify |
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* it under the terms of the GNU General Public License version 2 as |
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* published by the Free Software Foundation. |
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* |
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*/ |
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#include <linux/bootmem.h> |
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#include <linux/export.h> |
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#include <linux/highmem.h> |
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#include <asm/processor.h> |
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#include <asm/pgtable.h> |
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#include <asm/pgalloc.h> |
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#include <asm/tlbflush.h> |
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/* |
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* HIGHMEM API: |
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* |
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* kmap() API provides sleep semantics hence refered to as "permanent maps" |
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* It allows mapping LAST_PKMAP pages, using @last_pkmap_nr as the cursor |
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* for book-keeping |
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* |
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* kmap_atomic() can't sleep (calls pagefault_disable()), thus it provides |
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* shortlived ala "temporary mappings" which historically were implemented as |
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* fixmaps (compile time addr etc). Their book-keeping is done per cpu. |
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* |
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* Both these facts combined (preemption disabled and per-cpu allocation) |
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* means the total number of concurrent fixmaps will be limited to max |
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* such allocations in a single control path. Thus KM_TYPE_NR (another |
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* historic relic) is a small'ish number which caps max percpu fixmaps |
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* |
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* ARC HIGHMEM Details |
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* |
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* - the kernel vaddr space from 0x7z to 0x8z (currently used by vmalloc/module) |
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* is now shared between vmalloc and kmap (non overlapping though) |
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* |
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* - Both fixmap/pkmap use a dedicated page table each, hooked up to swapper PGD |
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* This means each only has 1 PGDIR_SIZE worth of kvaddr mappings, which means |
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* 2M of kvaddr space for typical config (8K page and 11:8:13 traversal split) |
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* |
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* - fixmap anyhow needs a limited number of mappings. So 2M kvaddr == 256 PTE |
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* slots across NR_CPUS would be more than sufficient (generic code defines |
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* KM_TYPE_NR as 20). |
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* |
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* - pkmap being preemptible, in theory could do with more than 256 concurrent |
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* mappings. However, generic pkmap code: map_new_virtual(), doesn't traverse |
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* the PGD and only works with a single page table @pkmap_page_table, hence |
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* sets the limit |
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*/ |
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extern pte_t * pkmap_page_table; |
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static pte_t * fixmap_page_table; |
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void *kmap(struct page *page) |
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{ |
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BUG_ON(in_interrupt()); |
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if (!PageHighMem(page)) |
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return page_address(page); |
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return kmap_high(page); |
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} |
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void *kmap_atomic(struct page *page) |
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{ |
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int idx, cpu_idx; |
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unsigned long vaddr; |
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preempt_disable(); |
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pagefault_disable(); |
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if (!PageHighMem(page)) |
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return page_address(page); |
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cpu_idx = kmap_atomic_idx_push(); |
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idx = cpu_idx + KM_TYPE_NR * smp_processor_id(); |
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vaddr = FIXMAP_ADDR(idx); |
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set_pte_at(&init_mm, vaddr, fixmap_page_table + idx, |
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mk_pte(page, kmap_prot)); |
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return (void *)vaddr; |
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} |
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EXPORT_SYMBOL(kmap_atomic); |
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void __kunmap_atomic(void *kv) |
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{ |
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unsigned long kvaddr = (unsigned long)kv; |
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if (kvaddr >= FIXMAP_BASE && kvaddr < (FIXMAP_BASE + FIXMAP_SIZE)) { |
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/* |
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* Because preemption is disabled, this vaddr can be associated |
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* with the current allocated index. |
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* But in case of multiple live kmap_atomic(), it still relies on |
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* callers to unmap in right order. |
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*/ |
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int cpu_idx = kmap_atomic_idx(); |
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int idx = cpu_idx + KM_TYPE_NR * smp_processor_id(); |
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WARN_ON(kvaddr != FIXMAP_ADDR(idx)); |
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pte_clear(&init_mm, kvaddr, fixmap_page_table + idx); |
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local_flush_tlb_kernel_range(kvaddr, kvaddr + PAGE_SIZE); |
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kmap_atomic_idx_pop(); |
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} |
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pagefault_enable(); |
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preempt_enable(); |
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} |
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EXPORT_SYMBOL(__kunmap_atomic); |
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static noinline pte_t * __init alloc_kmap_pgtable(unsigned long kvaddr) |
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{ |
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pgd_t *pgd_k; |
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pud_t *pud_k; |
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pmd_t *pmd_k; |
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pte_t *pte_k; |
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pgd_k = pgd_offset_k(kvaddr); |
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pud_k = pud_offset(pgd_k, kvaddr); |
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pmd_k = pmd_offset(pud_k, kvaddr); |
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pte_k = (pte_t *)alloc_bootmem_low_pages(PAGE_SIZE); |
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pmd_populate_kernel(&init_mm, pmd_k, pte_k); |
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return pte_k; |
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} |
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void __init kmap_init(void) |
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{ |
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/* Due to recursive include hell, we can't do this in processor.h */ |
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BUILD_BUG_ON(PAGE_OFFSET < (VMALLOC_END + FIXMAP_SIZE + PKMAP_SIZE)); |
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BUILD_BUG_ON(KM_TYPE_NR > PTRS_PER_PTE); |
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pkmap_page_table = alloc_kmap_pgtable(PKMAP_BASE); |
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BUILD_BUG_ON(LAST_PKMAP > PTRS_PER_PTE); |
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fixmap_page_table = alloc_kmap_pgtable(FIXMAP_BASE); |
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}
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