From f0293cd1f4fcc4fbdcd65a5a7b3b318a6d471f78 Mon Sep 17 00:00:00 2001 From: Mayuresh Chitale Date: Mon, 30 Jan 2023 13:18:15 +0530 Subject: [PATCH] riscv: mm: Implement pmdp_collapse_flush for THP When THP is enabled, 4K pages are collapsed into a single huge page using the generic pmdp_collapse_flush() which will further use flush_tlb_range() to shoot-down stale TLB entries. Unfortunately, the generic pmdp_collapse_flush() only invalidates cached leaf PTEs using address specific SFENCEs which results in repetitive (or unpredictable) page faults on RISC-V implementations which cache non-leaf PTEs. Provide a RISC-V specific pmdp_collapse_flush() which ensures both cached leaf and non-leaf PTEs are invalidated by using non-address specific SFENCEs as recommended by the RISC-V privileged specification. Fixes: e88b333142e4 ("riscv: mm: add THP support on 64-bit") Signed-off-by: Mayuresh Chitale Link: https://lore.kernel.org/r/20230130074815.1694055-1-mchitale@ventanamicro.com Signed-off-by: Palmer Dabbelt --- arch/riscv/include/asm/pgtable.h | 4 ++++ arch/riscv/mm/pgtable.c | 20 ++++++++++++++++++++ 2 files changed, 24 insertions(+) diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index 4eba9a9..3e01f4f 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -721,6 +721,10 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma, page_table_check_pmd_set(vma->vm_mm, address, pmdp, pmd); return __pmd(atomic_long_xchg((atomic_long_t *)pmdp, pmd_val(pmd))); } + +#define pmdp_collapse_flush pmdp_collapse_flush +extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, + unsigned long address, pmd_t *pmdp); #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ /* diff --git a/arch/riscv/mm/pgtable.c b/arch/riscv/mm/pgtable.c index 6645ead..fef4e73 100644 --- a/arch/riscv/mm/pgtable.c +++ b/arch/riscv/mm/pgtable.c @@ -81,3 +81,23 @@ int pmd_free_pte_page(pmd_t *pmd, unsigned long addr) } #endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */ +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, + unsigned long address, pmd_t *pmdp) +{ + pmd_t pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp); + + VM_BUG_ON(address & ~HPAGE_PMD_MASK); + VM_BUG_ON(pmd_trans_huge(*pmdp)); + /* + * When leaf PTE entries (regular pages) are collapsed into a leaf + * PMD entry (huge page), a valid non-leaf PTE is converted into a + * valid leaf PTE at the level 1 page table. Since the sfence.vma + * forms that specify an address only apply to leaf PTEs, we need a + * global flush here. collapse_huge_page() assumes these flushes are + * eager, so just do the fence here. + */ + flush_tlb_mm(vma->vm_mm); + return pmd; +} +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ -- 2.7.4