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KVM: remember position in kvm->vcpus array

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commit 8750e72a79dda2f665ce17b62049f4d62130d991 upstream.

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>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Radim Krčmář 2019-11-07 07:53:42 -05:00 committed by Greg Kroah-Hartman
parent 5163578e9d
commit b0c813fbbf
2 changed files with 6 additions and 10 deletions
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11
include/linux/kvm_host.h
View File

@ -266,7 +266,8 @@ 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;
@ -571,13 +572,7 @@ 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) \

5
virt/kvm/kvm_main.c
View File

@ -2864,7 +2864,8 @@ 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);
@ -2874,7 +2875,7 @@ 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