Exclusive table walks are the only supported table walk in the hyp, as
there is no construct like RCU available in the hypervisor code. Reject
any attempt to do a shared table walk by returning an error and allowing
the caller to clean up the mess.
Suggested-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
---
arch/arm64/include/asm/kvm_pgtable.h | 17 +++++++++++++++--
arch/arm64/kvm/hyp/pgtable.c | 5 ++++-
2 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 4b6b52ebc11c..d5cb01f8dc06 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -229,7 +229,18 @@ static inline kvm_pte_t *kvm_dereference_pteref(struct kvm_pgtable_walker *walke
return pteref;
}
-static inline void kvm_pgtable_walk_begin(struct kvm_pgtable_walker *walker) {}
+static inline int kvm_pgtable_walk_begin(struct kvm_pgtable_walker *walker)
+{
+ /*
+ * Due to the lack of RCU (or a similar protection scheme), only
+ * non-shared table walkers are allowed in the hypervisor.
+ */
+ if (walker->flags & KVM_PGTABLE_WALK_SHARED)
+ return -EPERM;
+
+ return 0;
+}
+
static inline void kvm_pgtable_walk_end(struct kvm_pgtable_walker *walker) {}
static inline bool kvm_pgtable_walk_lock_held(void)
@@ -247,10 +258,12 @@ static inline kvm_pte_t *kvm_dereference_pteref(struct kvm_pgtable_walker *walke
return rcu_dereference_check(pteref, !(walker->flags & KVM_PGTABLE_WALK_SHARED));
}
-static inline void kvm_pgtable_walk_begin(struct kvm_pgtable_walker *walker)
+static inline int kvm_pgtable_walk_begin(struct kvm_pgtable_walker *walker)
{
if (walker->flags & KVM_PGTABLE_WALK_SHARED)
rcu_read_lock();
+
+ return 0;
}
static inline void kvm_pgtable_walk_end(struct kvm_pgtable_walker *walker)
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index d6f3753cb87e..58dbe0ab567f 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -289,7 +289,10 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
};
int r;
- kvm_pgtable_walk_begin(walker);
+ r = kvm_pgtable_walk_begin(walker);
+ if (r)
+ return r;
+
r = _kvm_pgtable_walk(pgt, &walk_data);
kvm_pgtable_walk_end(walker);
--
2.38.1.584.g0f3c55d4c2-goog
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