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Subject[PATCH v4 02/14] KVM: arm64: Refcount hyp stage-1 pgtable pages
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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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