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authorHelge Deller <deller@gmx.de>2021-02-12 18:38:52 +0300
committerHelge Deller <deller@gmx.de>2021-02-12 18:39:42 +0300
commitb7795074a04669d0a023babf786d29bf67c68783 (patch)
tree5d4431b00e3416bc66f6fa1fc1a21cc530da4568 /arch/parisc/mm
parentae3c4761c15d96999d1aab6c57aedc3beb7fa004 (diff)
downloadlinux-b7795074a04669d0a023babf786d29bf67c68783.tar.xz
parisc: Optimize per-pagetable spinlocks
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>
Diffstat (limited to 'arch/parisc/mm')
-rw-r--r--arch/parisc/mm/hugetlbpage.c13
-rw-r--r--arch/parisc/mm/init.c10
2 files changed, 5 insertions, 18 deletions
diff --git a/arch/parisc/mm/hugetlbpage.c b/arch/parisc/mm/hugetlbpage.c
index d7ba014a7fbb..43652de5f139 100644
--- a/arch/parisc/mm/hugetlbpage.c
+++ b/arch/parisc/mm/hugetlbpage.c
@@ -142,24 +142,17 @@ static void __set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t entry)
{
- unsigned long flags;
-
- spin_lock_irqsave(pgd_spinlock((mm)->pgd), flags);
__set_huge_pte_at(mm, addr, ptep, entry);
- spin_unlock_irqrestore(pgd_spinlock((mm)->pgd), flags);
}
pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
pte_t *ptep)
{
- unsigned long flags;
pte_t entry;
- spin_lock_irqsave(pgd_spinlock((mm)->pgd), flags);
entry = *ptep;
__set_huge_pte_at(mm, addr, ptep, __pte(0));
- spin_unlock_irqrestore(pgd_spinlock((mm)->pgd), flags);
return entry;
}
@@ -168,29 +161,23 @@ pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
void huge_ptep_set_wrprotect(struct mm_struct *mm,
unsigned long addr, pte_t *ptep)
{
- unsigned long flags;
pte_t old_pte;
- spin_lock_irqsave(pgd_spinlock((mm)->pgd), flags);
old_pte = *ptep;
__set_huge_pte_at(mm, addr, ptep, pte_wrprotect(old_pte));
- spin_unlock_irqrestore(pgd_spinlock((mm)->pgd), flags);
}
int huge_ptep_set_access_flags(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep,
pte_t pte, int dirty)
{
- unsigned long flags;
int changed;
struct mm_struct *mm = vma->vm_mm;
- spin_lock_irqsave(pgd_spinlock((mm)->pgd), flags);
changed = !pte_same(*ptep, pte);
if (changed) {
__set_huge_pte_at(mm, addr, ptep, pte);
}
- spin_unlock_irqrestore(pgd_spinlock((mm)->pgd), flags);
return changed;
}
diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index 3ec633b11b54..9ca4e4ff6895 100644
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -37,11 +37,6 @@ extern int data_start;
extern void parisc_kernel_start(void); /* Kernel entry point in head.S */
#if CONFIG_PGTABLE_LEVELS == 3
-/* NOTE: This layout exactly conforms to the hybrid L2/L3 page table layout
- * with the first pmd adjacent to the pgd and below it. gcc doesn't actually
- * guarantee that global objects will be laid out in memory in the same order
- * as the order of declaration, so put these in different sections and use
- * the linker script to order them. */
pmd_t pmd0[PTRS_PER_PMD] __section(".data..vm0.pmd") __attribute__ ((aligned(PAGE_SIZE)));
#endif
@@ -559,6 +554,11 @@ void __init mem_init(void)
BUILD_BUG_ON(PGD_ENTRY_SIZE != sizeof(pgd_t));
BUILD_BUG_ON(PAGE_SHIFT + BITS_PER_PTE + BITS_PER_PMD + BITS_PER_PGD
> BITS_PER_LONG);
+#if CONFIG_PGTABLE_LEVELS == 3
+ BUILD_BUG_ON(PT_INITIAL > PTRS_PER_PMD);
+#else
+ BUILD_BUG_ON(PT_INITIAL > PTRS_PER_PGD);
+#endif
high_memory = __va((max_pfn << PAGE_SHIFT));
set_max_mapnr(max_low_pfn);