Messages in this thread | | | Subject | Re: [Patch v1 1/2] KVM: remember position in kvm->vcpus array | From | Nitesh Narayan Lal <> | Date | Wed, 6 Nov 2019 10:57:05 -0500 |
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On 11/6/19 9:43 AM, Sean Christopherson wrote: > On Wed, Nov 06, 2019 at 08:36:37AM -0500, Nitesh Narayan Lal wrote: >> 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> >> --- >> 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 719fc3e..31c4fde 100644 >> --- a/include/linux/kvm_host.h >> +++ b/include/linux/kvm_host.h >> @@ -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 vcpus_idx; /* index in kvm->vcpus array */ > I'd probably prefer vcpu_idx or vcpu_index, but it's not a strong > preference by any means.
Sure, I will probably replace it with vcpu_idx.
> >> 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->vcpus_idx; >> } >> >> #define kvm_for_each_memslot(memslot, slots) \ >> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c >> index 67ef3f2..24ab711 100644 >> --- a/virt/kvm/kvm_main.c >> +++ b/virt/kvm/kvm_main.c >> @@ -2673,7 +2673,10 @@ 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); >> + > Nit: I'd omit this newline since the assignment and BUG_ON() are directly > related.
Makes sense to me.
> >> + BUG_ON(kvm->vcpus[vcpu->vcpus_idx]); > The assignment to kvm->vcpus a few lines below should be updated to use > the new index.
Ah yes. Thanks for pointing this out.
> >> + >> >> /* Now it's all set up, let userspace reach it */ >> kvm_get_kvm(kvm); >> -- >> 1.8.3.1 >> -- Nitesh
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