Re: [PATCH v3 1/3] KVM: SVM: Refactor AVIC hardware setup logic into helper function

[Suthikulpanit, Suravee]

Hi Sean,

Thanks for the suggestion. I'll update this in v4.

Regards,
Suravee

On 12/31/2021 12:26 AM, Sean Christopherson wrote:
> On Mon, Dec 13, 2021, Suravee Suthikulpanit wrote:
> > To prepare for upcoming AVIC changes. There is no functional change.
> >
> > Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> > ---
> >   arch/x86/kvm/svm/avic.c | 10 ++++++++++
> >   arch/x86/kvm/svm/svm.c  |  8 +-------
> >   arch/x86/kvm/svm/svm.h  |  1 +
> >   3 files changed, 12 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> > index 8052d92069e0..63c3801d1829 100644
> > --- a/arch/x86/kvm/svm/avic.c
> > +++ b/arch/x86/kvm/svm/avic.c
> > @@ -1011,3 +1011,13 @@ void svm_vcpu_unblocking(struct kvm_vcpu *vcpu)
> >   		kvm_vcpu_update_apicv(vcpu);
> >   	avic_set_running(vcpu, true);
> >   }
> > +
> > +bool avic_hardware_setup(bool avic)
> > +{
> > +	if (!avic || !npt_enabled || !boot_cpu_has(X86_FEATURE_AVIC))
> > +		return false;
> > +
> > +	pr_info("AVIC enabled\n");
> > +	amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
> > +	return true;
> > +}
> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > index 989685098b3e..e59f663ab8cb 100644
> > --- a/arch/x86/kvm/svm/svm.c
> > +++ b/arch/x86/kvm/svm/svm.c
> > @@ -1031,13 +1031,7 @@ static __init int svm_hardware_setup(void)
> >   			nrips = false;
> >   	}
> >   
> > -	enable_apicv = avic = avic && npt_enabled && boot_cpu_has(X86_FEATURE_AVIC);
> > -
> > -	if (enable_apicv) {
> > -		pr_info("AVIC enabled\n");
> > -
> > -		amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
> > -	}
> > +	enable_apicv = avic = avic_hardware_setup(avic);
>
> Rather than pass in "avic", just do
>
> 	enable_apicv = avic == avic && avic_hardware_setup();
>
> This also conflicts with changes sitting in kvm/queue to nullify vcpu_(un)blocking
> when AVIC is disabled.  But moving AVIC setup to avic.c provides an opportunity for
> further cleanup, as it means vcpu_(un)blocking can be NULL by default and set to
> the AVIC helpers if and only if AVIC is enable.  That will allow making the helpers
> static in avic.c.  E.g.
>
> ---
>   arch/x86/kvm/svm/avic.c | 17 +++++++++++++++--
>   arch/x86/kvm/svm/svm.c  | 13 +------------
>   arch/x86/kvm/svm/svm.h  |  3 +--
>   3 files changed, 17 insertions(+), 16 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index 90364d02f22a..f5c6cab42d74 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -1027,7 +1027,7 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu)
>   	WRITE_ONCE(*(svm->avic_physical_id_cache), entry);
>   }
>
> -void avic_vcpu_blocking(struct kvm_vcpu *vcpu)
> +static void avic_vcpu_blocking(struct kvm_vcpu *vcpu)
>   {
>   	if (!kvm_vcpu_apicv_active(vcpu))
>   		return;
> @@ -1052,7 +1052,7 @@ void avic_vcpu_blocking(struct kvm_vcpu *vcpu)
>   	preempt_enable();
>   }
>
> -void avic_vcpu_unblocking(struct kvm_vcpu *vcpu)
> +static void avic_vcpu_unblocking(struct kvm_vcpu *vcpu)
>   {
>   	int cpu;
>
> @@ -1066,3 +1066,16 @@ void avic_vcpu_unblocking(struct kvm_vcpu *vcpu)
>
>   	put_cpu();
>   }
> +
> +bool avic_hardware_setup(struct kvm_x86_ops *x86_ops)
> +{
> +	if (!npt_enabled || !boot_cpu_has(X86_FEATURE_AVIC))
> +		return false;
> +
> +	x86_ops->vcpu_blocking = avic_vcpu_blocking,
> +	x86_ops->vcpu_unblocking = avic_vcpu_unblocking,
> +
> +	pr_info("AVIC enabled\n");
> +	amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
> +	return true;
> +}
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 6cb38044a860..6cb0f58238cd 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4390,8 +4390,6 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
>   	.prepare_guest_switch = svm_prepare_guest_switch,
>   	.vcpu_load = svm_vcpu_load,
>   	.vcpu_put = svm_vcpu_put,
> -	.vcpu_blocking = avic_vcpu_blocking,
> -	.vcpu_unblocking = avic_vcpu_unblocking,
>
>   	.update_exception_bitmap = svm_update_exception_bitmap,
>   	.get_msr_feature = svm_get_msr_feature,
> @@ -4674,16 +4672,7 @@ static __init int svm_hardware_setup(void)
>   			nrips = false;
>   	}
>
> -	enable_apicv = avic = avic && npt_enabled && boot_cpu_has(X86_FEATURE_AVIC);
> -
> -	if (enable_apicv) {
> -		pr_info("AVIC enabled\n");
> -
> -		amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
> -	} else {
> -		svm_x86_ops.vcpu_blocking = NULL;
> -		svm_x86_ops.vcpu_unblocking = NULL;
> -	}
> +	enable_apicv = avic = avic && avic_hardware_setup(&svm_x86_ops);
>
>   	if (vls) {
>   		if (!npt_enabled ||
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index daa8ca84afcc..59d91b969bd7 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -573,6 +573,7 @@ extern struct kvm_x86_nested_ops svm_nested_ops;
>
>   #define VMCB_AVIC_APIC_BAR_MASK		0xFFFFFFFFFF000ULL
>
> +bool avic_hardware_setup(struct kvm_x86_ops *ops);
>   int avic_ga_log_notifier(u32 ga_tag);
>   void avic_vm_destroy(struct kvm *kvm);
>   int avic_vm_init(struct kvm *kvm);
> @@ -593,8 +594,6 @@ int svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec);
>   bool svm_dy_apicv_has_pending_interrupt(struct kvm_vcpu *vcpu);
>   int svm_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
>   		       uint32_t guest_irq, bool set);
> -void avic_vcpu_blocking(struct kvm_vcpu *vcpu);
> -void avic_vcpu_unblocking(struct kvm_vcpu *vcpu);
>
>   /* sev.c */
>
> --