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KVM: remember position in kvm->vcpus array

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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>
This commit is contained in:
Radim Krčmář 2019-11-07 07:53:42 -05:00 committed by Paolo Bonzini
parent 662f1d1d19
commit 8750e72a79
2 changed files with 6 additions and 10 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

11
include/linux/kvm_host.h
View file

@ -266,7 +266,8 @@ struct kvm_vcpu {
struct preempt_notifier preempt_notifier; struct preempt_notifier preempt_notifier;
#endif #endif
int cpu; 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 srcu_idx;
int mode; int mode;
u64 requests; u64 requests;
@ -570,13 +571,7 @@ 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) static inline int kvm_vcpu_get_idx(struct kvm_vcpu *vcpu)
{ {
struct kvm_vcpu *tmp; return vcpu->vcpu_idx;
int idx;
kvm_for_each_vcpu(idx, tmp, vcpu->kvm)
if (tmp == vcpu)
return idx;
BUG();
} }
#define kvm_for_each_memslot(memslot, slots) \ #define kvm_for_each_memslot(memslot, slots) \

5
virt/kvm/kvm_main.c
View file

@ -2685,7 +2685,8 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
goto unlock_vcpu_destroy; 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 */ /* Now it's all set up, let userspace reach it */
kvm_get_kvm(kvm); kvm_get_kvm(kvm);
@ -2695,7 +2696,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
goto unlock_vcpu_destroy; 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 * Pairs with smp_rmb() in kvm_get_vcpu. Write kvm->vcpus