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    SubjectRe: [PATCH v4 04/21] KVM: arm64: Introduce helper to retrieve a PTE and its level
    On Mon, 9 Aug 2021 at 16:25, Quentin Perret <qperret@google.com> wrote:
    >
    > From: Marc Zyngier <maz@kernel.org>
    >
    > It is becoming a common need to fetch the PTE for a given address
    > together with its level. Add such a helper.
    >
    > Signed-off-by: Marc Zyngier <maz@kernel.org>
    > Signed-off-by: Quentin Perret <qperret@google.com>
    > ---
    > arch/arm64/include/asm/kvm_pgtable.h | 19 ++++++++++++++
    > arch/arm64/kvm/hyp/pgtable.c | 39 ++++++++++++++++++++++++++++
    > 2 files changed, 58 insertions(+)
    >
    > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
    > index f004c0115d89..082b9d65f40b 100644
    > --- a/arch/arm64/include/asm/kvm_pgtable.h
    > +++ b/arch/arm64/include/asm/kvm_pgtable.h
    > @@ -432,6 +432,25 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size);
    > int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
    > struct kvm_pgtable_walker *walker);
    >
    > +/**
    > + * kvm_pgtable_get_leaf() - Walk a page-table and retrieve the leaf entry
    > + * with its level.
    > + * @pgt: Page-table structure initialised by kvm_pgtable_*_init().
    > + * @addr: Input address for the start of the walk.
    > + * @ptep: Pointer to storage for the retrieved PTE.
    > + * @level: Pointer to storage for the level of the retrieved PTE.
    > + *
    > + * The offset of @addr within a page is ignored.
    > + *
    > + * The walker will walk the page-table entries corresponding to the input
    > + * address specified, retrieving the leaf corresponding to this address.
    > + * Invalid entries are treated as leaf entries.
    > + *
    > + * Return: 0 on success, negative error code on failure.
    > + */
    > +int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
    > + kvm_pte_t *ptep, u32 *level);
    > +
    > /**
    > * kvm_pgtable_stage2_find_range() - Find a range of Intermediate Physical
    > * Addresses with compatible permission
    > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
    > index 05321f4165e3..78f36bd5df6c 100644
    > --- a/arch/arm64/kvm/hyp/pgtable.c
    > +++ b/arch/arm64/kvm/hyp/pgtable.c
    > @@ -326,6 +326,45 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
    > return _kvm_pgtable_walk(&walk_data);
    > }
    >
    > +struct leaf_walk_data {
    > + kvm_pte_t pte;
    > + u32 level;
    > +};
    > +
    > +static int leaf_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
    > + enum kvm_pgtable_walk_flags flag, void * const arg)
    > +{
    > + struct leaf_walk_data *data = arg;
    > +
    > + data->pte = *ptep;
    > + data->level = level;
    > +
    > + return 0;
    > +}
    > +
    > +int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr,
    > + kvm_pte_t *ptep, u32 *level)
    > +{
    > + struct leaf_walk_data data;
    > + struct kvm_pgtable_walker walker = {
    > + .cb = leaf_walker,
    > + .flags = KVM_PGTABLE_WALK_LEAF,
    > + .arg = &data,
    > + };
    > + int ret;
    > +
    > + ret = kvm_pgtable_walk(pgt, ALIGN_DOWN(addr, PAGE_SIZE),
    > + PAGE_SIZE, &walker);
    > + if (!ret) {
    > + if (ptep)
    > + *ptep = data.pte;
    > + if (level)
    > + *level = data.level;
    > + }
    > +
    > + return ret;
    > +}
    > +
    > struct hyp_map_data {
    > u64 phys;
    > kvm_pte_t attr;
    > --
    > 2.32.0.605.g8dce9f2422-goog
    >

    Reviewed-by: Andrew Walbran <qwandor@google.com>
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