[PATCH] arm64: hugetlb: Restore TLB invalidation for BBM on contiguous ptes
From: Will Deacon <will@kernel.org>
Date: 2022-06-29 09:56:56
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
Commit fb396bb459c1 ("arm64/hugetlb: Drop TLB flush from get_clear_flush()")
removed TLB invalidation from get_clear_flush() [now get_clear_contig()]
on the basis that the core TLB invalidation code is aware of hugetlb
mappings backed by contiguous page-table entries and will cover the
correct virtual address range.
However, this change also resulted in the TLB invalidation being removed
from the "break" step in the break-before-make (BBM) sequence used
internally by huge_ptep_set_{access_flags,wrprotect}(), therefore
making the BBM sequence unsafe irrespective of later invalidation.
Although the architecture is desperately unclear about how exactly
contiguous ptes should be updated in a live page-table, restore TLB
invalidation to our BBM sequence under the assumption that BBM is the
right thing to be doing in the first place.
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Steve Capper <redacted>
Cc: Anshuman Khandual <redacted>
Cc: Mike Kravetz <redacted>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
Found by inspection.
arch/arm64/mm/hugetlbpage.c | 30 +++++++++++++++++++++---------
1 file changed, 21 insertions(+), 9 deletions(-)
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index e2a5ec9fdc0d..3618ef3f6d81 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c@@ -214,6 +214,19 @@ static pte_t get_clear_contig(struct mm_struct *mm, return orig_pte; } +static pte_t get_clear_contig_flush(struct mm_struct *mm, + unsigned long addr, + pte_t *ptep, + unsigned long pgsize, + unsigned long ncontig) +{ + pte_t orig_pte = get_clear_contig(mm, addr, ptep, pgsize, ncontig); + struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0); + + flush_tlb_range(&vma, addr, addr + (pgsize * ncontig)); + return orig_pte; +} + /* * Changing some bits of contiguous entries requires us to follow a * Break-Before-Make approach, breaking the whole contiguous set
@@ -447,19 +460,20 @@ int huge_ptep_set_access_flags(struct vm_area_struct *vma, int ncontig, i; size_t pgsize = 0; unsigned long pfn = pte_pfn(pte), dpfn; + struct mm_struct *mm = vma->vm_mm; pgprot_t hugeprot; pte_t orig_pte; if (!pte_cont(pte)) return ptep_set_access_flags(vma, addr, ptep, pte, dirty); - ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize); + ncontig = find_num_contig(mm, addr, ptep, &pgsize); dpfn = pgsize >> PAGE_SHIFT; if (!__cont_access_flags_changed(ptep, pte, ncontig)) return 0; - orig_pte = get_clear_contig(vma->vm_mm, addr, ptep, pgsize, ncontig); + orig_pte = get_clear_contig_flush(mm, addr, ptep, pgsize, ncontig); /* Make sure we don't lose the dirty or young state */ if (pte_dirty(orig_pte))
@@ -470,7 +484,7 @@ int huge_ptep_set_access_flags(struct vm_area_struct *vma, hugeprot = pte_pgprot(pte); for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn) - set_pte_at(vma->vm_mm, addr, ptep, pfn_pte(pfn, hugeprot)); + set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot)); return 1; }
@@ -492,7 +506,7 @@ void huge_ptep_set_wrprotect(struct mm_struct *mm, ncontig = find_num_contig(mm, addr, ptep, &pgsize); dpfn = pgsize >> PAGE_SHIFT; - pte = get_clear_contig(mm, addr, ptep, pgsize, ncontig); + pte = get_clear_contig_flush(mm, addr, ptep, pgsize, ncontig); pte = pte_wrprotect(pte); hugeprot = pte_pgprot(pte);
@@ -505,17 +519,15 @@ void huge_ptep_set_wrprotect(struct mm_struct *mm, pte_t huge_ptep_clear_flush(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep) { + struct mm_struct *mm = vma->vm_mm; size_t pgsize; int ncontig; - pte_t orig_pte; if (!pte_cont(READ_ONCE(*ptep))) return ptep_clear_flush(vma, addr, ptep); - ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize); - orig_pte = get_clear_contig(vma->vm_mm, addr, ptep, pgsize, ncontig); - flush_tlb_range(vma, addr, addr + pgsize * ncontig); - return orig_pte; + ncontig = find_num_contig(mm, addr, ptep, &pgsize); + return get_clear_contig_flush(mm, addr, ptep, pgsize, ncontig); } static int __init hugetlbpage_init(void)
--
2.37.0.rc0.161.g10f37bed90-goog
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel