Huacai,
On 2024/10/12 上午10:16, Huacai Chen wrote:
Hi, Bibo,
On Thu, Oct 10, 2024 at 11:50 AM Bibo Mao <maobibo@xxxxxxxxxxx> wrote:
For kernel space area on LoongArch system, both two consecutive page
table entries should be enabled with PAGE_GLOBAL bit. So with function
set_pte() and pte_clear(), pte buddy entry is checked and set besides
its own pte entry. However it is not atomic operation to set both two
pte entries, there is problem with test_vmalloc test case.
With previous patch, all page table entries are set with PAGE_GLOBAL
bit at beginning. Only its own pte entry need update with function
set_pte() and pte_clear(), nothing to do with buddy pte entry.
Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
---
arch/loongarch/include/asm/pgtable.h | 44 ++++++++++------------------
1 file changed, 15 insertions(+), 29 deletions(-)
diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
index 22e3a8f96213..4be3f0dbecda 100644
--- a/arch/loongarch/include/asm/pgtable.h
+++ b/arch/loongarch/include/asm/pgtable.h
@@ -325,40 +325,26 @@ extern void paging_init(void);
static inline void set_pte(pte_t *ptep, pte_t pteval)
{
WRITE_ONCE(*ptep, pteval);
+}
- if (pte_val(pteval) & _PAGE_GLOBAL) {
- pte_t *buddy = ptep_buddy(ptep);
- /*
- * Make sure the buddy is global too (if it's !none,
- * it better already be global)
- */
- if (pte_none(ptep_get(buddy))) {
-#ifdef CONFIG_SMP
- /*
- * For SMP, multiple CPUs can race, so we need
- * to do this atomically.
- */
- __asm__ __volatile__(
- __AMOR "$zero, %[global], %[buddy] \n"
- : [buddy] "+ZB" (buddy->pte)
- : [global] "r" (_PAGE_GLOBAL)
- : "memory");
-
- DBAR(0b11000); /* o_wrw = 0b11000 */
-#else /* !CONFIG_SMP */
- WRITE_ONCE(*buddy, __pte(pte_val(ptep_get(buddy)) | _PAGE_GLOBAL));
-#endif /* CONFIG_SMP */
- }
- }
+static inline unsigned long __ptep_get_and_clear(pte_t *ptep)
+{
+ return atomic64_fetch_and(_PAGE_GLOBAL, (atomic64_t *)&pte_val(*ptep));
}
static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
{
- /* Preserve global status for the pair */
- if (pte_val(ptep_get(ptep_buddy(ptep))) & _PAGE_GLOBAL)
- set_pte(ptep, __pte(_PAGE_GLOBAL));
- else
- set_pte(ptep, __pte(0));
+ __ptep_get_and_clear(ptep);
With the first patch, a kernel pte always take _PAGE_GLOBAL, so we
don't need an expensive atomic operation, just
"set_pte(pte_val(ptep_get(ptep)) & _PAGE_GLOBAL)" is OK here. And then
we don't need a custom ptep_get_and_clear().
Will use non-atomic method and test again, also will remove customed
function ptep_get_and_clear().
Regards
Bibo Mao
Huacai
+}
+
+#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
+static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
+ unsigned long addr, pte_t *ptep)
+{
+ unsigned long val;
+
+ val = __ptep_get_and_clear(ptep);
+ return __pte(val);
}
#define PGD_T_LOG2 (__builtin_ffs(sizeof(pgd_t)) - 1)
--
2.39.3
