[PATCH v4 06/11] powerpc/mm/book3s64/hash: Applies counting method to monitor lockless pgtbl walks

Leonardo Bras
2019-09-27T23:41:31Z

Applies the counting-based method for monitoring all hash-related functions
that do lockless pagetable walks.

hash_page_mm: Adds comment that explain that there is no need to
local_int_disable/save given that it is only called from DataAccess
interrupt, so interrupts are already disabled.

Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
---
arch/powerpc/mm/book3s64/hash_tlb.c | 2 ++
arch/powerpc/mm/book3s64/hash_utils.c | 12 +++++++++++-
2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/book3s64/hash_tlb.c b/arch/powerpc/mm/book3s64/hash_tlb.c
index 4a70d8dd39cd..5e5213c3f7c4 100644
--- a/arch/powerpc/mm/book3s64/hash_tlb.c
+++ b/arch/powerpc/mm/book3s64/hash_tlb.c
@@ -209,6 +209,7 @@ void __flush_hash_table_range(struct mm_struct *mm, unsigned long start,
* to being hashed). This is not the most performance oriented
* way to do things but is fine for our needs here.
*/
+ start_lockless_pgtbl_walk(mm);
local_irq_save(flags);
arch_enter_lazy_mmu_mode();
for (; start < end; start += PAGE_SIZE) {
@@ -230,6 +231,7 @@ void __flush_hash_table_range(struct mm_struct *mm, unsigned long start,
}
arch_leave_lazy_mmu_mode();
local_irq_restore(flags);
+ end_lockless_pgtbl_walk(mm);
}

void flush_tlb_pmd_range(struct mm_struct *mm, pmd_t *pmd, unsigned long addr)
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index b8ad14bb1170..8615fab87c43 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -1321,7 +1321,11 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea,
ea &= ~((1ul << mmu_psize_defs[psize].shift) - 1);
#endif /* CONFIG_PPC_64K_PAGES */

- /* Get PTE and page size from page tables */
+ /* Get PTE and page size from page tables :
+ * Called in from DataAccess interrupt (data_access_common: 0x300),
+ * interrupts are disabled here.
+ */
+ start_lockless_pgtbl_walk(mm);
ptep = find_linux_pte(pgdir, ea, &is_thp, &hugeshift);
if (ptep == NULL || !pte_present(*ptep)) {
DBG_LOW(" no PTE !\n");
@@ -1438,6 +1442,7 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea,
DBG_LOW(" -> rc=%d\n", rc);

bail:
+ end_lockless_pgtbl_walk(mm);
exception_exit(prev_state);
return rc;
}
@@ -1547,10 +1552,12 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
vsid = get_user_vsid(&mm->context, ea, ssize);
if (!vsid)
return;
+
/*
* Hash doesn't like irqs. Walking linux page table with irq disabled
* saves us from holding multiple locks.
*/
+ start_lockless_pgtbl_walk(mm);
local_irq_save(flags);

/*
@@ -1597,6 +1604,7 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
pte_val(*ptep));
out_exit:
local_irq_restore(flags);
+ end_lockless_pgtbl_walk(mm);
}

#ifdef CONFIG_PPC_MEM_KEYS
@@ -1613,11 +1621,13 @@ u16 get_mm_addr_key(struct mm_struct *mm, unsigned long address)
if (!mm || !mm->pgd)
return 0;

+ start_lockless_pgtbl_walk(mm);
local_irq_save(flags);
ptep = find_linux_pte(mm->pgd, address, NULL, NULL);
if (ptep)
pkey = pte_to_pkey_bits(pte_val(READ_ONCE(*ptep)));
local_irq_restore(flags);
+ end_lockless_pgtbl_walk(mm);

return pkey;
}
--
2.20.1