Hi Gavin,
On 8/15/21 2:59 AM, Gavin Shan wrote:
> This adds inline helper kvm_check_async_pf_completion_queue() to
> check if there are pending completion in the queue. The empty stub
> is also added on !CONFIG_KVM_ASYNC_PF so that the caller needn't
> consider if CONFIG_KVM_ASYNC_PF is enabled.
>
> All checks on the completion queue is done by the newly added inline
> function since list_empty() and list_empty_careful() are interchangeable.
why is it interchangeable?
>
> Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 2 +-
> include/linux/kvm_host.h | 10 ++++++++++
> virt/kvm/async_pf.c | 10 +++++-----
> virt/kvm/kvm_main.c | 4 +---
> 4 files changed, 17 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index e5d5c5ed7dd4..7f35d9324b99 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -11591,7 +11591,7 @@ static inline bool kvm_guest_apic_has_interrupt(struct kvm_vcpu *vcpu)
>
> static inline bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
> {
> - if (!list_empty_careful(&vcpu->async_pf.done))
> + if (kvm_check_async_pf_completion_queue(vcpu))
> return true;
>
> if (kvm_apic_has_events(vcpu))
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 85b61a456f1c..a5f990f6dc35 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -339,12 +339,22 @@ struct kvm_async_pf {
> bool notpresent_injected;
> };
>
> +static inline bool kvm_check_async_pf_completion_queue(struct kvm_vcpu *vcpu)
> +{
> + return !list_empty_careful(&vcpu->async_pf.done);
> +}
> +
> void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu);
> void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu);
> bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
> unsigned long hva, struct kvm_arch_async_pf *arch);
> int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
> #else
> +static inline bool kvm_check_async_pf_completion_queue(struct kvm_vcpu *vcpu)
> +{
> + return false;
> +}
> +
> static inline void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu) { }
> #endif
>
> diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
> index dd777688d14a..d145a61a046a 100644
> --- a/virt/kvm/async_pf.c
> +++ b/virt/kvm/async_pf.c
> @@ -70,7 +70,7 @@ static void async_pf_execute(struct work_struct *work)
> kvm_arch_async_page_present(vcpu, apf);
>
> spin_lock(&vcpu->async_pf.lock);
> - first = list_empty(&vcpu->async_pf.done);
> + first = !kvm_check_async_pf_completion_queue(vcpu);
> list_add_tail(&apf->link, &vcpu->async_pf.done);
> apf->vcpu = NULL;
> spin_unlock(&vcpu->async_pf.lock);
> @@ -122,7 +122,7 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
> spin_lock(&vcpu->async_pf.lock);
> }
>
> - while (!list_empty(&vcpu->async_pf.done)) {
> + while (kvm_check_async_pf_completion_queue(vcpu)) {
this is replaced by a stronger check. Please can you explain why is it
equivalent?
> struct kvm_async_pf *work =
> list_first_entry(&vcpu->async_pf.done,
> typeof(*work), link);
> @@ -138,7 +138,7 @@ void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
> {
> struct kvm_async_pf *work;
>
> - while (!list_empty_careful(&vcpu->async_pf.done) &&
> + while (kvm_check_async_pf_completion_queue(vcpu) &&
> kvm_arch_can_dequeue_async_page_present(vcpu)) {
> spin_lock(&vcpu->async_pf.lock);
> work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
> @@ -205,7 +205,7 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
> struct kvm_async_pf *work;
> bool first;
>
> - if (!list_empty_careful(&vcpu->async_pf.done))
> + if (kvm_check_async_pf_completion_queue(vcpu))
> return 0;
>
> work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
> @@ -216,7 +216,7 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
> INIT_LIST_HEAD(&work->queue); /* for list_del to work */
>
> spin_lock(&vcpu->async_pf.lock);
> - first = list_empty(&vcpu->async_pf.done);
> + first = !kvm_check_async_pf_completion_queue(vcpu);
> list_add_tail(&work->link, &vcpu->async_pf.done);
> spin_unlock(&vcpu->async_pf.lock);
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index b50dbe269f4b..8795503651b1 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3282,10 +3282,8 @@ static bool vcpu_dy_runnable(struct kvm_vcpu *vcpu)
> if (kvm_arch_dy_runnable(vcpu))
> return true;
>
> -#ifdef CONFIG_KVM_ASYNC_PF
> - if (!list_empty_careful(&vcpu->async_pf.done))
> + if (kvm_check_async_pf_completion_queue(vcpu))
> return true;
> -#endif
>
> return false;
> }
>
Thanks
Eric
