linux-kernel - Re: [v4 2/4] arm64: kvm: add kvm cpu hotplug

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Date:	Tue, 26 May 2015 10:35:11 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	AKASHI Takahiro <takahiro.akashi@...aro.org>,
	catalin.marinas@....com, will.deacon@....com, mark.rutland@....com
CC:	linux-arm-kernel@...ts.infradead.org,
	linaro-kernel@...ts.linaro.org, geoff@...radead.org,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	broonie@...nel.org, david.griego@...aro.org,
	christoffer.dall@...aro.org, freddy77@...il.com
Subject: Re: [v4 2/4] arm64: kvm: add kvm cpu hotplug

On 08/05/15 02:18, AKASHI Takahiro wrote:
> This patch allows cpu cores to be up and down by adding
> kvm_arch_hardware_enable/isable(). This way, especially in kexec case,
> cores are reset to initial states and kexec can gracefully shutdown the
> system and reboot a new kernel from EL2.
> 
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
> ---
>  arch/arm/include/asm/kvm_host.h   |    1 -
>  arch/arm/kvm/arm.c                |   29 +++++++++++++++++++----------
>  arch/arm64/include/asm/kvm_host.h |    1 -
>  3 files changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 41008cd..ca97764 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -237,7 +237,6 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
>  
>  struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
>  
> -static inline void kvm_arch_hardware_disable(void) {}
>  static inline void kvm_arch_hardware_unsetup(void) {}
>  static inline void kvm_arch_sync_events(struct kvm *kvm) {}
>  static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 251ab9e..e989925 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -87,11 +87,6 @@ struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void)
>  	return &kvm_arm_running_vcpu;
>  }
>  
> -int kvm_arch_hardware_enable(void)
> -{
> -	return 0;
> -}
> -
>  int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
>  {
>  	return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
> @@ -885,6 +880,9 @@ static void cpu_init_hyp_mode(void *dummy)

Since you removed the IPI, why do you keep the dummy argument?

>  	unsigned long stack_page;
>  	unsigned long vector_ptr;
>  
> +	if (__hyp_get_vectors() != hyp_default_vectors)
> +		return;
> +
>  	/* Switch from the HYP stub to our own HYP init vector */
>  	__hyp_set_vectors(kvm_get_idmap_vector());
>  
> @@ -921,6 +919,10 @@ static int hyp_init_cpu_notify(struct notifier_block *self,
>  		if (__hyp_get_vectors() == hyp_default_vectors)
>  			cpu_init_hyp_mode(NULL);
>  		break;
> +	case CPU_DYING:
> +	case CPU_DYING_FROZEN:
> +		kvm_cpu_reset(NULL);
> +		break;
>  	}
>  
>  	return NOTIFY_OK;
> @@ -936,6 +938,7 @@ static int hyp_init_cpu_pm_notifier(struct notifier_block *self,
>  				    void *v)
>  {
>  	if (cmd == CPU_PM_EXIT &&
> +	    kvm_arm_get_running_vcpu() &&
>  	    __hyp_get_vectors() == hyp_default_vectors) {
>  		cpu_init_hyp_mode(NULL);
>  		return NOTIFY_OK;
> @@ -1039,11 +1042,6 @@ static int init_hyp_mode(void)
>  	}
>  
>  	/*
> -	 * Execute the init code on each CPU.
> -	 */
> -	on_each_cpu(cpu_init_hyp_mode, NULL, 1);
> -
> -	/*
>  	 * Init HYP view of VGIC
>  	 */
>  	err = kvm_vgic_hyp_init();
> @@ -1144,6 +1142,17 @@ out_err:
>  	return err;
>  }
>  
> +int kvm_arch_hardware_enable(void)
> +{
> +	cpu_init_hyp_mode(NULL);
> +	return 0;
> +}
> +
> +void kvm_arch_hardware_disable(void)
> +{
> +	kvm_cpu_reset(NULL);
> +}
> +

Bahhh... Just rename cpu_init_hyp_mode to kvm_arch_hardware_enable, and
kvM_cpu_reset to kvm_arch_hardware_disable. I don't see the point of
keeping this indirection.

>  /* NOP: Compiling as a module not supported */
>  void kvm_arch_exit(void)
>  {
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 6a8da9c..831e6a4 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -262,7 +262,6 @@ static inline void vgic_arch_setup(const struct vgic_params *vgic)
>  	}
>  }
>  
> -static inline void kvm_arch_hardware_disable(void) {}
>  static inline void kvm_arch_hardware_unsetup(void) {}
>  static inline void kvm_arch_sync_events(struct kvm *kvm) {}
>  static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
> 


-- 
Jazz is not dead. It just smells funny...
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