Re: [PATCH RFC v3 3/9] KVM: remember position in kvm->vcpus array

Cornelia Huck
2017-08-29T11:31:08Z

On Mon, 21 Aug 2017 22:35:24 +0200
Radim Krčmář <rkrcmar@redhat.com> wrote:

> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
> ---
> include/linux/kvm_host.h | 11 +++--------
> virt/kvm/kvm_main.c | 5 ++++-
> 2 files changed, 7 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 6882538eda32..a8ff956616d2 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -220,7 +220,8 @@ struct kvm_vcpu {
> struct preempt_notifier preempt_notifier;
> #endif
> int cpu;
> - int vcpu_id;
> + int vcpu_id; /* id given by userspace at creation */
> + int vcpus_idx; /* index in kvm->vcpus array */

I predict confusion in the future over which is which... maybe
s/vcpus_idx/vcpus_array_pos/ or something like that?

> int srcu_idx;
> int mode;
> unsigned long requests;
> @@ -516,13 +517,7 @@ static inline struct kvm_vcpu *kvm_get_vcpu_by_id(struct kvm *kvm, int id)
>
> static inline int kvm_vcpu_get_idx(struct kvm_vcpu *vcpu)
> {
> - struct kvm_vcpu *tmp;
> - int idx;
> -
> - kvm_for_each_vcpu(idx, tmp, vcpu->kvm)
> - if (tmp == vcpu)
> - return idx;
> - BUG();
> + return vcpu->vcpus_idx;
> }
>
> #define kvm_for_each_memslot(memslot, slots) \
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index e17c40d986f3..caf8323f7df7 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2498,7 +2498,10 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
> goto unlock_vcpu_destroy;
> }
>
> - BUG_ON(kvm->vcpus[atomic_read(&kvm->online_vcpus)]);
> + vcpu->vcpus_idx = atomic_read(&kvm->online_vcpus);
> +
> + BUG_ON(kvm->vcpus[vcpu->vcpus_idx]);
> +
>
> /* Now it's all set up, let userspace reach it */
> kvm_get_kvm(kvm);

I like the concept.