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

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Date:   Wed, 28 Feb 2018 15:39:55 -0500
From:   Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
To:     David Hildenbrand <david@...hat.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 02/28/2018 04:44 AM, David Hildenbrand wrote:
> 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?
I haven't considered that, do you have any suggestions?
>