On Sun, Aug 19, 2018 at 08:17:45AM +0800, Wei Yang wrote:
> update_memslots() is only called by __kvm_set_memory_region(), in which
> change is calculated to indicate the following behavior. With this
What is the 'following behavior' you mention?
> information, it is not necessary to do the calculation again in
> update_memslots().
>
> By encoding the number of slot adjustment in the lowest byte of change,
> the slots->used_slots adjustment is accomplished by one addition.
>
> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
> ---
> include/linux/kvm_host.h | 11 +++++++----
> virt/kvm/kvm_main.c | 14 ++++----------
> 2 files changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 4ee7bc548a83..e0ae6cf82c0d 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -610,12 +610,15 @@ id_to_memslot(struct kvm_memslots *slots, int id)
> *
> * Since flags can be changed by some of these operations, the following
> * differentiation is the best we can do for __kvm_set_memory_region():
> + *
> + * Encode the number of slot adjustment in the lowest byte, which will
> + * be used in update_memslots().
> */
> enum kvm_mr_change {
> - KVM_MR_CREATE,
> - KVM_MR_DELETE,
> - KVM_MR_MOVE,
> - KVM_MR_FLAGS_ONLY,
> + KVM_MR_CREATE = 0x0001,
> + KVM_MR_DELETE = 0x00ff,
> + KVM_MR_MOVE = 0x0000,
> + KVM_MR_FLAGS_ONLY = 0x0100,
> };
>
> int kvm_set_memory_region(struct kvm *kvm,
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 3d233ebfbee9..5c1911790f25 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -801,21 +801,15 @@ static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot)
> * sorted array and known changed memslot position.
> */
> static void update_memslots(struct kvm_memslots *slots,
> - struct kvm_memory_slot *new)
> + struct kvm_memory_slot *new,
> + enum kvm_mr_change change)
> {
> int id = new->id;
> int i = slots->id_to_index[id];
> struct kvm_memory_slot *mslots = slots->memslots;
>
> WARN_ON(mslots[i].id != id);
> - if (!new->npages) {
> - WARN_ON(!mslots[i].npages);
> - if (mslots[i].npages)
> - slots->used_slots--;
> - } else {
> - if (!mslots[i].npages)
> - slots->used_slots++;
> - }
> + slots->used_slots += (char)change;
>
> while (i < KVM_MEM_SLOTS_NUM - 1 &&
> new->base_gfn <= mslots[i + 1].base_gfn) {
> @@ -1050,7 +1044,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
> memset(&new.arch, 0, sizeof(new.arch));
> }
>
> - update_memslots(slots, &new);
> + update_memslots(slots, &new, change);
> old_memslots = install_new_memslots(kvm, as_id, slots);
>
> kvm_arch_commit_memory_region(kvm, mem, &old, &new, change);
> --
> 2.15.1
>
