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

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.

Fixes: fb396bb459c1 ("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>

diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index e2a5ec9..3618ef3 100644 (file)
--- 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)