b7795074a0
On parisc a spinlock is stored in the next page behind the pgd which
protects against parallel accesses to the pgd. That's why one additional
page (PGD_ALLOC_ORDER) is allocated for the pgd.
Matthew Wilcox suggested that we instead should use a pointer in the
struct page table for this spinlock and noted, that the comments for the
PGD_ORDER and PMD_ORDER defines were wrong.
Both suggestions are addressed with this patch. Instead of having an own
spinlock to protect the pgd, we now switch to use the existing
page_table_lock. Additionally, beside loading the pgd into cr25 in
switch_mm_irqs_off(), the physical address of this lock is loaded into
cr28 (tr4), so that we can avoid implementing a complicated lookup in
assembly for this lock in the TLB fault handlers.
The existing Hybrid L2/L3 page table scheme (where the pmd is adjacent
to the pgd) has been dropped with this patch.
Remove the locking in set_pte() and the huge-page pte functions too.
They trigger a spinlock recursion on 32bit machines and seem unnecessary.
Suggested-by: Matthew Wilcox <willy@infradead.org>
Fixes: b37d1c1898b2 ("parisc: Use per-pagetable spinlock")
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
75 lines
1.7 KiB
C
75 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_PGALLOC_H
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#define _ASM_PGALLOC_H
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#include <linux/gfp.h>
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#include <linux/mm.h>
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#include <linux/threads.h>
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#include <asm/processor.h>
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#include <asm/fixmap.h>
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#include <asm/cache.h>
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#define __HAVE_ARCH_PMD_ALLOC_ONE
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#define __HAVE_ARCH_PMD_FREE
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#define __HAVE_ARCH_PGD_FREE
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#include <asm-generic/pgalloc.h>
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/* Allocate the top level pgd (page directory) */
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static inline pgd_t *pgd_alloc(struct mm_struct *mm)
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{
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pgd_t *pgd;
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pgd = (pgd_t *) __get_free_pages(GFP_KERNEL, PGD_ORDER);
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if (unlikely(pgd == NULL))
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return NULL;
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memset(pgd, 0, PAGE_SIZE << PGD_ORDER);
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return pgd;
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}
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static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
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{
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free_pages((unsigned long)pgd, PGD_ORDER);
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}
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#if CONFIG_PGTABLE_LEVELS == 3
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/* Three Level Page Table Support for pmd's */
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static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
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{
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set_pud(pud, __pud((PxD_FLAG_PRESENT | PxD_FLAG_VALID) +
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(__u32)(__pa((unsigned long)pmd) >> PxD_VALUE_SHIFT)));
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}
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static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
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{
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pmd_t *pmd;
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pmd = (pmd_t *)__get_free_pages(GFP_PGTABLE_KERNEL, PMD_ORDER);
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if (likely(pmd))
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memset ((void *)pmd, 0, PAGE_SIZE << PMD_ORDER);
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return pmd;
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}
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static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
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{
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free_pages((unsigned long)pmd, PMD_ORDER);
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}
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#endif
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static inline void
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pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd, pte_t *pte)
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{
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set_pmd(pmd, __pmd((PxD_FLAG_PRESENT | PxD_FLAG_VALID)
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+ (__u32)(__pa((unsigned long)pte) >> PxD_VALUE_SHIFT)));
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}
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#define pmd_populate(mm, pmd, pte_page) \
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pmd_populate_kernel(mm, pmd, page_address(pte_page))
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#define pmd_pgtable(pmd) pmd_page(pmd)
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#endif
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