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Commit b0c813fb authored by Radim Krčmář's avatar Radim Krčmář Committed by Greg Kroah-Hartman
Browse files

KVM: remember position in kvm->vcpus array 



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: default avatarRadim Krčmář <rkrcmar@redhat.com>
Signed-off-by: default avatarNitesh Narayan Lal <nitesh@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
[borntraeger@de.ibm.com]: backport to 4.19 (also fits for 5.4)
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5163578e

include/linux/kvm_host.h

+3 −8
Original line number Diff line number Diff line
@@ -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)	\

virt/kvm/kvm_main.c

+3 −2
Original line number Diff line number Diff line
@@ -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