linux-kernel - Re: [PATCH v2 08/15] KVM: s390: interface to enable AP execution mode

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Date:   Wed, 28 Feb 2018 10:44:29 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        cohuck@...hat.com, kwankhede@...dia.com,
        bjsdjshi@...ux.vnet.ibm.com, pbonzini@...hat.com,
        alex.williamson@...hat.com, pmorel@...ux.vnet.ibm.com,
        alifm@...ux.vnet.ibm.com, mjrosato@...ux.vnet.ibm.com,
        jjherne@...ux.vnet.ibm.com, thuth@...hat.com,
        pasic@...ux.vnet.ibm.com, fiuczy@...ux.vnet.ibm.com,
        buendgen@...ibm.com
Subject: Re: [PATCH v2 08/15] KVM: s390: interface to enable AP execution mode

On 27.02.2018 15:28, Tony Krowiak wrote:
> Introduces a new interface to enable AP interpretive
> execution (IE) mode for the KVM guest. When running
> with IE mode enabled, AP instructions executed on the
> KVM guest will be interpreted by the firmware and
> passed directly through to an AP device installed on
> the system. The CPU model feature for AP must
> be enabled for the KVM guest in order to enable
> interpretive execution mode.
> 
> This interface will be used in a subsequent patch
> by the VFIO AP device driver.
> 
> Signed-off-by: Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
> ---
>  arch/s390/include/asm/kvm-ap.h   |    2 ++
>  arch/s390/include/asm/kvm_host.h |    1 +
>  arch/s390/kvm/kvm-ap.c           |   27 +++++++++++++++++++++++++++
>  arch/s390/kvm/kvm-s390.h         |    1 +
>  4 files changed, 31 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/s390/include/asm/kvm-ap.h b/arch/s390/include/asm/kvm-ap.h
> index 46e7c5b..6bd6bfb 100644
> --- a/arch/s390/include/asm/kvm-ap.h
> +++ b/arch/s390/include/asm/kvm-ap.h
> @@ -51,4 +51,6 @@ struct kvm_ap_matrix {
>  
>  void kvm_ap_deconfigure_matrix(struct kvm *kvm);
>  
> +int kvm_ap_enable_ie_mode(struct kvm *kvm);
> +
>  #endif /* _ASM_KVM_AP */
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index a4c77d3..1eebdd6 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -186,6 +186,7 @@ struct kvm_s390_sie_block {
>  #define ECA_AIV		0x00200000
>  #define ECA_VX		0x00020000
>  #define ECA_PROTEXCI	0x00002000
> +#define ECA_APIE	0x00000008
>  #define ECA_SII		0x00000001
>  	__u32	eca;			/* 0x004c */
>  #define ICPT_INST	0x04
> diff --git a/arch/s390/kvm/kvm-ap.c b/arch/s390/kvm/kvm-ap.c
> index bb29045..862e54b 100644
> --- a/arch/s390/kvm/kvm-ap.c
> +++ b/arch/s390/kvm/kvm-ap.c
> @@ -307,3 +307,30 @@ void kvm_ap_deconfigure_matrix(struct kvm *kvm)
>  	kvm_ap_clear_crycb_masks(kvm);
>  }
>  EXPORT_SYMBOL(kvm_ap_deconfigure_matrix);
> +
> +/**
> + * kvm_ap_enable_ie_mode
> + *
> + * Enable interpretrive execution of AP instructions for the guest. When
> + * enabled, AP instructions executed on the guest will be interpreted and
> + * passed through to an AP installed on the host system.
> + *
> + * Returns 0 if interpretrive execution is enabled. Returns -EOPNOTSUPP
> + * if AP facilities are not installed for the guest.
> + *
> + * @kvm: the guest's kvm structure
> + */
> +int kvm_ap_enable_ie_mode(struct kvm *kvm)
> +{
> +	int i;
> +	struct kvm_vcpu *vcpu;
> +
> +	if (!test_kvm_cpu_feat(kvm, KVM_S390_VM_CPU_FEAT_AP))
> +		return -EOPNOTSUPP;
> +
> +	kvm_for_each_vcpu(i, vcpu, kvm)
> +		vcpu->arch.sie_block->eca |= ECA_APIE;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(kvm_ap_enable_ie_mode);
> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
> index 1b5621f..3142541 100644
> --- a/arch/s390/kvm/kvm-s390.h
> +++ b/arch/s390/kvm/kvm-s390.h
> @@ -18,6 +18,7 @@
>  #include <asm/facility.h>
>  #include <asm/processor.h>
>  #include <asm/sclp.h>
> +#include <asm/ap.h>
>  
>  /* Transactional Memory Execution related macros */
>  #define IS_TE_ENABLED(vcpu)	((vcpu->arch.sie_block->ecb & ECB_TE))
> 

And also, what about hot-plugged CPUs?

-- 

Thanks,

David / dhildenb