On 04.11.2021 01:25, Sean Christopherson wrote:
From: Maciej S. Szmigiero <maciej.szmigiero@xxxxxxxxxx>
Memslot ID to the corresponding memslot mappings are currently kept as
indices in static id_to_index array.
The size of this array depends on the maximum allowed memslot count
(regardless of the number of memslots actually in use).
This has become especially problematic recently, when memslot count cap was
removed, so the maximum count is now full 32k memslots - the maximum
allowed by the current KVM API.
Keeping these IDs in a hash table (instead of an array) avoids this
problem.
Resolving a memslot ID to the actual memslot (instead of its index) will
also enable transitioning away from an array-based implementation of the
whole memslots structure in a later commit.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@xxxxxxxxxx>
Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
include/linux/kvm_host.h | 16 +++----
virt/kvm/kvm_main.c | 96 +++++++++++++++++++++++++++++++---------
2 files changed, 84 insertions(+), 28 deletions(-)
(..)
@@ -1259,17 +1257,49 @@ static int kvm_alloc_dirty_bitmap(struct kvm_memory_slot *memslot)
return 0;
}
+static void kvm_replace_memslot(struct kvm_memslots *slots,
+ struct kvm_memory_slot *old,
+ struct kvm_memory_slot *new)
+{
+ /*
+ * Remove the old memslot from the hash list, copying the node data
+ * would corrupt the list.
+ */
+ if (old) {
+ hash_del(&old->id_node);
+
+ if (!new)
+ return;
+ }
+
+ /* Copy the source *data*, not the pointer, to the destination. */
+ if (old)
+ *new = *old;
This way of writing it (that, is re-checking whether "old" is not-NULL)
suggests that it could have been set to NULL inside the previous block
(since the last check), which isn't true.
Thanks,
Maciej
