Hi Jisheng,
On 31/12/2023 07:21, Alexandre Ghiti wrote:
Hi Jisheng,
On 19/12/2023 18:50, Jisheng Zhang wrote:
If non-leaf PTEs I.E pmd, pud or p4d is modified, a sfence.vma is
a must for safe, imagine if an implementation caches the non-leaf
translation in TLB, although I didn't meet this HW so far, but it's
possible in theory.
Signed-off-by: Jisheng Zhang<jszhang@xxxxxxxxxx>
---
arch/riscv/include/asm/pgalloc.h | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)
diff --git a/arch/riscv/include/asm/pgalloc.h
b/arch/riscv/include/asm/pgalloc.h
index d169a4f41a2e..a12fb83fa1f5 100644
--- a/arch/riscv/include/asm/pgalloc.h
+++ b/arch/riscv/include/asm/pgalloc.h
@@ -95,7 +95,13 @@ static inline void pud_free(struct mm_struct *mm,
pud_t *pud)
__pud_free(mm, pud);
}
-#define __pud_free_tlb(tlb, pud, addr) pud_free((tlb)->mm, pud)
+#define __pud_free_tlb(tlb, pud, addr) \
+do { \
+ if (pgtable_l4_enabled) { \
+ pagetable_pud_dtor(virt_to_ptdesc(pud)); \
+ tlb_remove_page_ptdesc((tlb), virt_to_ptdesc(pud)); \
The specification indeed states that an sfence.vma must be emitted
after a page directory modification. Your change is not enough though
since eventually tlb_flush() is called and in this function we should
add:
if (tlb->freed_tables)
tlb_flush_mm();
I sent a patch for that here
https://lore.kernel.org/linux-riscv/20240128120405.25876-1-alexghiti@xxxxxxxxxxxx/
You can add:
Reviewed-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Thanks,
Alex
otherwise we are not guaranteed that a "global" sfence.vma is called.
Would you be able to benchmark this change and see the performance
impact?
Thanks,
Alex
+ } \
+} while (0)
#define p4d_alloc_one p4d_alloc_one
static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned
long addr)
@@ -124,7 +130,11 @@ static inline void p4d_free(struct mm_struct
*mm, p4d_t *p4d)
__p4d_free(mm, p4d);
}
-#define __p4d_free_tlb(tlb, p4d, addr) p4d_free((tlb)->mm, p4d)
+#define __p4d_free_tlb(tlb, p4d, addr) \
+do { \
+ if (pgtable_l5_enabled) \
+ tlb_remove_page_ptdesc((tlb), virt_to_ptdesc(p4d)); \
+} while (0)
#endif /* __PAGETABLE_PMD_FOLDED */
static inline void sync_kernel_mappings(pgd_t *pgd)
@@ -149,7 +159,11 @@ static inline pgd_t *pgd_alloc(struct mm_struct
*mm)
#ifndef __PAGETABLE_PMD_FOLDED
-#define __pmd_free_tlb(tlb, pmd, addr) pmd_free((tlb)->mm, pmd)
+#define __pmd_free_tlb(tlb, pmd, addr) \
+do { \
+ pagetable_pmd_dtor(virt_to_ptdesc(pmd)); \
+ tlb_remove_page_ptdesc((tlb), virt_to_ptdesc(pmd)); \
+} while (0)
#endif /* __PAGETABLE_PMD_FOLDED */
