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    Subject[PATCH v4 02/14] KVM: arm64: Refcount hyp stage-1 pgtable pages
    From
    To prepare the ground for allowing hyp stage-1 mappings to be removed at
    run-time, update the KVM page-table code to maintain a correct refcount
    using the ->{get,put}_page() function callbacks.

    Signed-off-by: Quentin Perret <qperret@google.com>
    ---
    arch/arm64/kvm/hyp/pgtable.c | 39 ++++++++++++++++++------------------
    1 file changed, 19 insertions(+), 20 deletions(-)

    diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
    index f8ceebe4982e..e50e9158fc56 100644
    --- a/arch/arm64/kvm/hyp/pgtable.c
    +++ b/arch/arm64/kvm/hyp/pgtable.c
    @@ -383,21 +383,6 @@ enum kvm_pgtable_prot kvm_pgtable_hyp_pte_prot(kvm_pte_t pte)
    return prot;
    }

    -static bool hyp_pte_needs_update(kvm_pte_t old, kvm_pte_t new)
    -{
    - /*
    - * Tolerate KVM recreating the exact same mapping, or changing software
    - * bits if the existing mapping was valid.
    - */
    - if (old == new)
    - return false;
    -
    - if (!kvm_pte_valid(old))
    - return true;
    -
    - return !WARN_ON((old ^ new) & ~KVM_PTE_LEAF_ATTR_HI_SW);
    -}
    -
    static bool hyp_map_walker_try_leaf(u64 addr, u64 end, u32 level,
    kvm_pte_t *ptep, struct hyp_map_data *data)
    {
    @@ -407,11 +392,16 @@ static bool hyp_map_walker_try_leaf(u64 addr, u64 end, u32 level,
    if (!kvm_block_mapping_supported(addr, end, phys, level))
    return false;

    + data->phys += granule;
    new = kvm_init_valid_leaf_pte(phys, data->attr, level);
    - if (hyp_pte_needs_update(old, new))
    - smp_store_release(ptep, new);
    + if (old == new)
    + return true;
    + if (!kvm_pte_valid(old))
    + data->mm_ops->get_page(ptep);
    + else if (WARN_ON((old ^ new) & ~KVM_PTE_LEAF_ATTR_HI_SW))
    + return false;

    - data->phys += granule;
    + smp_store_release(ptep, new);
    return true;
    }

    @@ -433,6 +423,7 @@ static int hyp_map_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
    return -ENOMEM;

    kvm_set_table_pte(ptep, childp, mm_ops);
    + mm_ops->get_page(ptep);
    return 0;
    }

    @@ -482,8 +473,16 @@ static int hyp_free_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
    enum kvm_pgtable_walk_flags flag, void * const arg)
    {
    struct kvm_pgtable_mm_ops *mm_ops = arg;
    + kvm_pte_t pte = *ptep;
    +
    + if (!kvm_pte_valid(pte))
    + return 0;
    +
    + mm_ops->put_page(ptep);
    +
    + if (kvm_pte_table(pte, level))
    + mm_ops->put_page(kvm_pte_follow(pte, mm_ops));

    - mm_ops->put_page((void *)kvm_pte_follow(*ptep, mm_ops));
    return 0;
    }

    @@ -491,7 +490,7 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt)
    {
    struct kvm_pgtable_walker walker = {
    .cb = hyp_free_walker,
    - .flags = KVM_PGTABLE_WALK_TABLE_POST,
    + .flags = KVM_PGTABLE_WALK_LEAF | KVM_PGTABLE_WALK_TABLE_POST,
    .arg = pgt->mm_ops,
    };

    --
    2.34.1.173.g76aa8bc2d0-goog
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