2019-06-04 16:11:33 +08:00
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// SPDX-License-Identifier: GPL-2.0-only
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2015-03-09 21:23:49 +08:00
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/*
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* Copyright (C) 2015 Synopsys, Inc. (www.synopsys.com)
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*/
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2018-10-31 06:09:49 +08:00
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#include <linux/memblock.h>
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2015-03-09 21:23:49 +08:00
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#include <linux/export.h>
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#include <linux/highmem.h>
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2020-06-09 12:32:38 +08:00
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#include <linux/pgtable.h>
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2020-06-09 12:32:42 +08:00
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#include <asm/processor.h>
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2015-03-09 21:23:49 +08:00
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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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2016-02-24 07:24:55 +08:00
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* kmap() API provides sleep semantics hence referred to as "permanent maps"
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2015-03-09 21:23:49 +08:00
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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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2020-11-03 17:27:21 +08:00
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* - The fixed KMAP slots for kmap_local/atomic() require KM_MAX_IDX slots per
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* CPU. So the number of CPUs sharing a single PTE page is limited.
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2015-03-09 21:23:49 +08:00
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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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2015-12-19 16:13:34 +08:00
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static noinline pte_t * __init alloc_kmap_pgtable(unsigned long kvaddr)
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2015-03-09 21:23:49 +08:00
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{
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2020-06-09 12:33:05 +08:00
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pmd_t *pmd_k = pmd_off_k(kvaddr);
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2015-03-09 21:23:49 +08:00
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pte_t *pte_k;
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2018-10-31 06:08:54 +08:00
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pte_k = (pte_t *)memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
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2019-03-12 14:30:31 +08:00
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if (!pte_k)
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panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
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__func__, PAGE_SIZE, PAGE_SIZE);
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2015-03-09 21:23:49 +08:00
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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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2015-12-19 16:13:34 +08:00
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void __init kmap_init(void)
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2015-03-09 21:23:49 +08:00
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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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2020-11-03 17:27:21 +08:00
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BUILD_BUG_ON(LAST_PKMAP > PTRS_PER_PTE);
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BUILD_BUG_ON(FIX_KMAP_SLOTS > PTRS_PER_PTE);
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2015-03-09 21:23:49 +08:00
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pkmap_page_table = alloc_kmap_pgtable(PKMAP_BASE);
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2020-11-03 17:27:21 +08:00
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alloc_kmap_pgtable(FIXMAP_BASE);
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2015-03-09 21:23:49 +08:00
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}
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