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SubjectRe: [PATCH 1/2] KVM: x86: extract guest running logic from __vcpu_run
On Fri, Feb 6, 2015 at 4:16 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> Rename the old __vcpu_run to vcpu_run, and extract its main logic
> to a new function.
>
> The next patch will add a new early-exit condition to __vcpu_run,
> avoid extra indentation.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---

Reviewed-by: David Matlack <dmatlack@google.com>

> arch/x86/kvm/x86.c | 67 +++++++++++++++++++++++++++++-------------------------
> 1 file changed, 36 insertions(+), 31 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index bd7a70be41b3..0b8dd13676ef 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6165,7 +6165,7 @@ void kvm_arch_mmu_notifier_invalidate_page(struct kvm *kvm,
> }
>
> /*
> - * Returns 1 to let __vcpu_run() continue the guest execution loop without
> + * Returns 1 to let vcpu_run() continue the guest execution loop without
> * exiting to the userspace. Otherwise, the value will be returned to the
> * userspace.
> */
> @@ -6383,42 +6383,45 @@ out:
> return r;
> }
>
> +static inline int __vcpu_run(struct kvm *kvm, struct kvm_vcpu *vcpu)

Kind of confusing function body given the name. Maybe put

if (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
!vcpu->arch.apf.halted)
return vcpu_enter_guest(vcpu);

back in vcpu_run and rename this function? vcpu_wait?

> +{
> + if (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
> + !vcpu->arch.apf.halted)
> + return vcpu_enter_guest(vcpu);
> +
> + srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_block(vcpu);
> + vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> + if (!kvm_check_request(KVM_REQ_UNHALT, vcpu))
> + return 1;
>
> -static int __vcpu_run(struct kvm_vcpu *vcpu)
> + kvm_apic_accept_events(vcpu);
> + switch(vcpu->arch.mp_state) {
> + case KVM_MP_STATE_HALTED:
> + vcpu->arch.pv.pv_unhalted = false;
> + vcpu->arch.mp_state =
> + KVM_MP_STATE_RUNNABLE;
> + case KVM_MP_STATE_RUNNABLE:
> + vcpu->arch.apf.halted = false;
> + break;
> + case KVM_MP_STATE_INIT_RECEIVED:
> + break;
> + default:
> + return -EINTR;
> + break;
> + }
> + return 1;
> +}
> +
> +static int vcpu_run(struct kvm_vcpu *vcpu)

vcpu_run_loop might be a clearer name.

> {
> int r;
> struct kvm *kvm = vcpu->kvm;
>
> vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
>
> - r = 1;
> - while (r > 0) {
> - if (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
> - !vcpu->arch.apf.halted)
> - r = vcpu_enter_guest(vcpu);
> - else {
> - srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> - kvm_vcpu_block(vcpu);
> - vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> - if (kvm_check_request(KVM_REQ_UNHALT, vcpu)) {
> - kvm_apic_accept_events(vcpu);
> - switch(vcpu->arch.mp_state) {
> - case KVM_MP_STATE_HALTED:
> - vcpu->arch.pv.pv_unhalted = false;
> - vcpu->arch.mp_state =
> - KVM_MP_STATE_RUNNABLE;
> - case KVM_MP_STATE_RUNNABLE:
> - vcpu->arch.apf.halted = false;
> - break;
> - case KVM_MP_STATE_INIT_RECEIVED:
> - break;
> - default:
> - r = -EINTR;
> - break;
> - }
> - }
> - }
> -
> + for (;;) {
> + r = __vcpu_run(kvm, vcpu);
> if (r <= 0)
> break;
>
> @@ -6430,6 +6433,7 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
> r = -EINTR;
> vcpu->run->exit_reason = KVM_EXIT_INTR;
> ++vcpu->stat.request_irq_exits;
> + break;
> }
>
> kvm_check_async_pf_completion(vcpu);
> @@ -6438,6 +6442,7 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
> r = -EINTR;
> vcpu->run->exit_reason = KVM_EXIT_INTR;
> ++vcpu->stat.signal_exits;
> + break;

The removal of the loop condition and the addition of these "break"s
change the loop behavior slightly, but I think it's safe. We'll start
breaking before checking need_resched(), but we're about to return to
userspace anyway so we'll reschedule then.

> }
> if (need_resched()) {
> srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> @@ -6569,7 +6574,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> } else
> WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
>
> - r = __vcpu_run(vcpu);
> + r = vcpu_run(vcpu);
>
> out:
> post_kvm_run_save(vcpu);
> --
> 1.8.3.1
>
>


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