From: Radim Krčmář rkrcmar@redhat.com
Fetching an index for any vcpu in kvm->vcpus array by traversing the entire array everytime is costly. This patch remembers the position of each vcpu in kvm->vcpus array by storing it in vcpus_idx under kvm_vcpu structure.
Signed-off-by: Radim Krčmář rkrcmar@redhat.com Signed-off-by: Nitesh Narayan Lal nitesh@redhat.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com [borntraeger@de.ibm.com]: backport to 4.19 (also fits for 5.4) Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com --- include/linux/kvm_host.h | 11 +++-------- virt/kvm/kvm_main.c | 5 +++-- 2 files changed, 6 insertions(+), 10 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 8dd4ebb58e97..827f70ce0b49 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -248,7 +248,8 @@ struct kvm_vcpu { struct preempt_notifier preempt_notifier; #endif int cpu; - int vcpu_id; + int vcpu_id; /* id given by userspace at creation */ + int vcpu_idx; /* index in kvm->vcpus array */ int srcu_idx; int mode; u64 requests; @@ -551,13 +552,7 @@ 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->vcpu_idx; }
#define kvm_for_each_memslot(memslot, slots) \ diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a3d82113ae1c..86ef740763b5 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2751,7 +2751,8 @@ 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->vcpu_idx = atomic_read(&kvm->online_vcpus); + BUG_ON(kvm->vcpus[vcpu->vcpu_idx]);
/* Now it's all set up, let userspace reach it */ kvm_get_kvm(kvm); @@ -2761,7 +2762,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) goto unlock_vcpu_destroy; }
- kvm->vcpus[atomic_read(&kvm->online_vcpus)] = vcpu; + kvm->vcpus[vcpu->vcpu_idx] = vcpu;
/* * Pairs with smp_rmb() in kvm_get_vcpu. Write kvm->vcpus