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: b37d1c1898 ("parisc: Use per-pagetable spinlock")
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
100 lines
2.3 KiB
C
100 lines
2.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __PARISC_MMU_CONTEXT_H
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#define __PARISC_MMU_CONTEXT_H
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/atomic.h>
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#include <linux/spinlock.h>
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#include <asm-generic/mm_hooks.h>
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/* on PA-RISC, we actually have enough contexts to justify an allocator
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* for them. prumpf */
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extern unsigned long alloc_sid(void);
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extern void free_sid(unsigned long);
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#define init_new_context init_new_context
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static inline int
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init_new_context(struct task_struct *tsk, struct mm_struct *mm)
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{
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BUG_ON(atomic_read(&mm->mm_users) != 1);
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mm->context = alloc_sid();
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return 0;
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}
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#define destroy_context destroy_context
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static inline void
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destroy_context(struct mm_struct *mm)
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{
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free_sid(mm->context);
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mm->context = 0;
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}
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static inline unsigned long __space_to_prot(mm_context_t context)
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{
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#if SPACEID_SHIFT == 0
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return context << 1;
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#else
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return context >> (SPACEID_SHIFT - 1);
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#endif
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}
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static inline void load_context(mm_context_t context)
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{
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mtsp(context, 3);
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mtctl(__space_to_prot(context), 8);
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}
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static inline void switch_mm_irqs_off(struct mm_struct *prev,
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struct mm_struct *next, struct task_struct *tsk)
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{
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if (prev != next) {
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#ifdef CONFIG_TLB_PTLOCK
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/* put physical address of page_table_lock in cr28 (tr4)
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for TLB faults */
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spinlock_t *pgd_lock = &next->page_table_lock;
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mtctl(__pa(__ldcw_align(&pgd_lock->rlock.raw_lock)), 28);
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#endif
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mtctl(__pa(next->pgd), 25);
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load_context(next->context);
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}
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}
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static inline void switch_mm(struct mm_struct *prev,
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struct mm_struct *next, struct task_struct *tsk)
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{
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unsigned long flags;
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if (prev == next)
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return;
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local_irq_save(flags);
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switch_mm_irqs_off(prev, next, tsk);
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local_irq_restore(flags);
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}
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#define switch_mm_irqs_off switch_mm_irqs_off
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#define activate_mm activate_mm
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static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next)
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{
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/*
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* Activate_mm is our one chance to allocate a space id
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* for a new mm created in the exec path. There's also
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* some lazy tlb stuff, which is currently dead code, but
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* we only allocate a space id if one hasn't been allocated
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* already, so we should be OK.
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*/
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BUG_ON(next == &init_mm); /* Should never happen */
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if (next->context == 0)
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next->context = alloc_sid();
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switch_mm(prev,next,current);
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}
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#include <asm-generic/mmu_context.h>
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#endif
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