[PATCH] MIPS: make userspace mapping young by default

Huang Pei
2021-02-04T01:41:14Z

MIPS page fault path(except huge page) takes 3 exceptions (1 TLB Miss
+ 2 TLB Invalid), butthe second TLB Invalid exception is just
triggered by __update_tlb from do_page_fault writing tlb without
_PAGE_VALID set. With this patch, user space mapping prot is made
young by default (with both _PAGE_VALID and _PAGE_YOUNG set),
and it only take 1 TLB Miss + 1 TLB Invalid exception

Remove pte_sw_mkyoung without polluting MM code and make page fault
delay of MIPS on par with other architecture

Signed-off-by: Huang Pei <huangpei@loongson.cn>
---
arch/mips/mm/cache.c | 30 ++++++++++++++++--------------
include/linux/pgtable.h | 8 --------
mm/memory.c | 3 ---
3 files changed, 16 insertions(+), 25 deletions(-)

diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
index 23b16bfd97b2..e19cf424bb39 100644
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -156,29 +156,31 @@ unsigned long _page_cachable_default;
EXPORT_SYMBOL(_page_cachable_default);

#define PM(p) __pgprot(_page_cachable_default | (p))
+#define PVA(p) PM(_PAGE_VALID | _PAGE_ACCESSED | (p))

static inline void setup_protection_map(void)
{
protection_map[0] = PM(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
- protection_map[1] = PM(_PAGE_PRESENT | _PAGE_NO_EXEC);
- protection_map[2] = PM(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
- protection_map[3] = PM(_PAGE_PRESENT | _PAGE_NO_EXEC);
- protection_map[4] = PM(_PAGE_PRESENT);
- protection_map[5] = PM(_PAGE_PRESENT);
- protection_map[6] = PM(_PAGE_PRESENT);
- protection_map[7] = PM(_PAGE_PRESENT);
+ protection_map[1] = PVA(_PAGE_PRESENT | _PAGE_NO_EXEC);
+ protection_map[2] = PVA(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
+ protection_map[3] = PVA(_PAGE_PRESENT | _PAGE_NO_EXEC);
+ protection_map[4] = PVA(_PAGE_PRESENT);
+ protection_map[5] = PVA(_PAGE_PRESENT);
+ protection_map[6] = PVA(_PAGE_PRESENT);
+ protection_map[7] = PVA(_PAGE_PRESENT);

protection_map[8] = PM(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
- protection_map[9] = PM(_PAGE_PRESENT | _PAGE_NO_EXEC);
- protection_map[10] = PM(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE |
+ protection_map[9] = PVA(_PAGE_PRESENT | _PAGE_NO_EXEC);
+ protection_map[10] = PVA(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE |
_PAGE_NO_READ);
- protection_map[11] = PM(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE);
- protection_map[12] = PM(_PAGE_PRESENT);
- protection_map[13] = PM(_PAGE_PRESENT);
- protection_map[14] = PM(_PAGE_PRESENT | _PAGE_WRITE);
- protection_map[15] = PM(_PAGE_PRESENT | _PAGE_WRITE);
+ protection_map[11] = PVA(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE);
+ protection_map[12] = PVA(_PAGE_PRESENT);
+ protection_map[13] = PVA(_PAGE_PRESENT);
+ protection_map[14] = PVA(_PAGE_PRESENT);
+ protection_map[15] = PVA(_PAGE_PRESENT);
}

+#undef _PVA
#undef PM

void cpu_cache_init(void)
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 8fcdfa52eb4b..8c042627399a 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -432,14 +432,6 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
* To be differentiate with macro pte_mkyoung, this macro is used on platforms
* where software maintains page access bit.
*/
-#ifndef pte_sw_mkyoung
-static inline pte_t pte_sw_mkyoung(pte_t pte)
-{
- return pte;
-}
-#define pte_sw_mkyoung pte_sw_mkyoung
-#endif
-
#ifndef pte_savedwrite
#define pte_savedwrite pte_write
#endif
diff --git a/mm/memory.c b/mm/memory.c
index feff48e1465a..95718a623884 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2890,7 +2890,6 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
}
flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
entry = mk_pte(new_page, vma->vm_page_prot);
- entry = pte_sw_mkyoung(entry);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);

/*
@@ -3548,7 +3547,6 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
__SetPageUptodate(page);

entry = mk_pte(page, vma->vm_page_prot);
- entry = pte_sw_mkyoung(entry);
if (vma->vm_flags & VM_WRITE)
entry = pte_mkwrite(pte_mkdirty(entry));

@@ -3824,7 +3822,6 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct page *page)

flush_icache_page(vma, page);
entry = mk_pte(page, vma->vm_page_prot);
- entry = pte_sw_mkyoung(entry);
if (write)
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
/* copy-on-write page */
--
2.17.1