linux-kernel - Re: [PATCH v4 01/15] KVM: async_pf: Move struct kvm_async

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Date:   Wed, 10 Nov 2021 16:37:51 +0100
From:   Eric Auger <eauger@...hat.com>
To:     Gavin Shan <gshan@...hat.com>, kvmarm@...ts.cs.columbia.edu
Cc:     kvm@...r.kernel.org, maz@...nel.org, linux-kernel@...r.kernel.org,
        shan.gavin@...il.com, Jonathan.Cameron@...wei.com,
        pbonzini@...hat.com, vkuznets@...hat.com, will@...nel.org
Subject: Re: [PATCH v4 01/15] KVM: async_pf: Move struct kvm_async_pf around

Hi Gavin,

On 8/15/21 2:59 AM, Gavin Shan wrote:
> This moves the definition of "struct kvm_async_pf" and the related
> functions after "struct kvm_vcpu" so that newly added inline functions
> in the subsequent patches can dereference "struct kvm_vcpu" properly.
> Otherwise, the unexpected build error will be raised:
> 
>    error: dereferencing pointer to incomplete type ‘struct kvm_vcpu’
>    return !list_empty_careful(&vcpu->async_pf.done);
>                                    ^~
> Since we're here, the sepator between type and field in "struct kvm_vcpu"
separator
> is replaced by tab. The empty stub kvm_check_async_pf_completion() is also
> added on !CONFIG_KVM_ASYNC_PF, which is needed by subsequent patches to
> support asynchronous page fault on ARM64.
> 
> Signed-off-by: Gavin Shan <gshan@...hat.com>
> ---
>  include/linux/kvm_host.h | 44 +++++++++++++++++++++-------------------
>  1 file changed, 23 insertions(+), 21 deletions(-)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index ae7735b490b4..85b61a456f1c 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -199,27 +199,6 @@ int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
>  struct kvm_io_device *kvm_io_bus_get_dev(struct kvm *kvm, enum kvm_bus bus_idx,
>  					 gpa_t addr);
>  
> -#ifdef CONFIG_KVM_ASYNC_PF
> -struct kvm_async_pf {
> -	struct work_struct work;
> -	struct list_head link;
> -	struct list_head queue;
> -	struct kvm_vcpu *vcpu;
> -	struct mm_struct *mm;
> -	gpa_t cr2_or_gpa;
> -	unsigned long addr;
> -	struct kvm_arch_async_pf arch;
> -	bool   wakeup_all;
> -	bool notpresent_injected;
> -};
> -
> -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);
> -#endif
> -
>  #ifdef KVM_ARCH_WANT_MMU_NOTIFIER
>  struct kvm_gfn_range {
>  	struct kvm_memory_slot *slot;
> @@ -346,6 +325,29 @@ struct kvm_vcpu {
>  	struct kvm_dirty_ring dirty_ring;
>  };
>  
> +#ifdef CONFIG_KVM_ASYNC_PF
> +struct kvm_async_pf {
> +	struct work_struct		work;
> +	struct list_head		link;
> +	struct list_head		queue;
> +	struct kvm_vcpu			*vcpu;
> +	struct mm_struct		*mm;
> +	gpa_t				cr2_or_gpa;
> +	unsigned long			addr;
> +	struct kvm_arch_async_pf	arch;
> +	bool				wakeup_all;
> +	bool				notpresent_injected;
> +};
> +
> +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 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu) { }
why is that stub needed on ARM64 and not on the other archs?

Eric
> +#endif
> +
>  /* must be called with irqs disabled */
>  static __always_inline void guest_enter_irqoff(void)
>  {
>