Re: [PART1 RFC v3 02/12] KVM: x86: Introducing kvm_x86_ops VM init/uninit hooks

[Paolo Bonzini <pbonzini@redhat.com>]

On 18/03/2016 07:09, Suravee Suthikulpanit wrote:
> Adding function pointers in struct kvm_x86_ops for processor-specific
> layer to provide hooks for when KVM initialize and un-initialize VM.

This is not the only thing your patch is doing, and the "other" change
definitely needs a lot more explanation about why you did it and how you
audited the code to ensure that it is safe.

Paolo

> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> ---
>  arch/x86/include/asm/kvm_host.h |  3 +++
>  arch/x86/kvm/x86.c              | 10 +++++++++-
>  virt/kvm/kvm_main.c             |  8 ++++----
>  3 files changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 44adbb8..4b0dd0f 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -828,6 +828,9 @@ struct kvm_x86_ops {
>  	bool (*cpu_has_high_real_mode_segbase)(void);
>  	void (*cpuid_update)(struct kvm_vcpu *vcpu);
>  
> +	int (*vm_init)(struct kvm *kvm);
> +	void (*vm_uninit)(struct kvm *kvm);
> +
>  	/* Create, but do not attach this VCPU */
>  	struct kvm_vcpu *(*vcpu_create)(struct kvm *kvm, unsigned id);
>  	void (*vcpu_free)(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 429c3f5..4d2961d 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7700,6 +7700,8 @@ void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu)
>  
>  int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>  {
> +	int ret = 0;
> +
>  	if (type)
>  		return -EINVAL;
>  
> @@ -7724,7 +7726,10 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>  	INIT_DELAYED_WORK(&kvm->arch.kvmclock_update_work, kvmclock_update_fn);
>  	INIT_DELAYED_WORK(&kvm->arch.kvmclock_sync_work, kvmclock_sync_fn);
>  
> -	return 0;
> +	if (kvm_x86_ops->vm_init)
> +		ret = kvm_x86_ops->vm_init(kvm);
> +
> +	return ret;
>  }
>  
>  static void kvm_unload_vcpu_mmu(struct kvm_vcpu *vcpu)
> @@ -7751,6 +7756,9 @@ static void kvm_free_vcpus(struct kvm *kvm)
>  	kvm_for_each_vcpu(i, vcpu, kvm)
>  		kvm_arch_vcpu_free(vcpu);
>  
> +	if (kvm_x86_ops->vm_uninit)
> +		kvm_x86_ops->vm_uninit(kvm);
> +
>  	mutex_lock(&kvm->lock);
>  	for (i = 0; i < atomic_read(&kvm->online_vcpus); i++)
>  		kvm->vcpus[i] = NULL;
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 1ca0258..5460325 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -536,10 +536,6 @@ static struct kvm *kvm_create_vm(unsigned long type)
>  	if (!kvm)
>  		return ERR_PTR(-ENOMEM);
>  
> -	r = kvm_arch_init_vm(kvm, type);
> -	if (r)
> -		goto out_err_no_disable;
> -
>  	r = hardware_enable_all();
>  	if (r)
>  		goto out_err_no_disable;
> @@ -578,6 +574,10 @@ static struct kvm *kvm_create_vm(unsigned long type)
>  	atomic_set(&kvm->users_count, 1);
>  	INIT_LIST_HEAD(&kvm->devices);
>  
> +	r = kvm_arch_init_vm(kvm, type);
> +	if (r)
> +		goto out_err;
> +
>  	r = kvm_init_mmu_notifier(kvm);
>  	if (r)
>  		goto out_err;
>