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arm64: hugetlb: Restore TLB invalidation for BBM on contiguous ptes

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Commit fb396bb459 ("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.

Fixes: fb396bb459 ("arm64/hugetlb: Drop TLB flush from get_clear_flush()")
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Steve Capper <steve.capper@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Marc Zyngier <maz@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20220629095349.25748-1-will@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Will Deacon 2022-06-29 10:53:49 +01:00 committed by Catalin Marinas
parent c50f11c619
commit 4109823037
1 changed files with 21 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
arch/arm64/mm/hugetlbpage.c
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@ -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)