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    SubjectRe: [PATCH v2 08/15] KVM: s390: interface to enable AP execution mode
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    On 03/01/2018 04:35 AM, David Hildenbrand wrote:
    > On 28.02.2018 21:39, Tony Krowiak wrote:
    >> 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@linux.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?
    > You should handle the KVM_S390_VM_CPU_FEAT_AP feature instead during
    > kvm_arch_vcpu_setup(), independent of any configured AP devices.
    >
    > This avoids the races I mentioned in regards to this series and also
    > will handle hotplugged CPUs properly.
    >
    > If KVM_S390_VM_CPU_FEAT_AP is configured for a guest -> each CPU sets
    > ECA_APIE during kvm_arch_vcpu_setup().
    >
    >
    > (In the vSIE code, simply allow to set ECA_APIE in the shadow SCB in
    > case KVM_S390_VM_CPU_FEAT_AP is enabled)
    Patch series v3 will be posted very shortly, but I thought I'd give you a
    heads up concerning what is forthcoming with regard to ECA_APIE. I'm
    adding a device attribute to the KVM_S390_VM_CRYPTO group for setting a
    flag via the KVM_SET_DEVICE_ATTR ioctl. The flag indicates whether
    ECA_APIE should be set or not. The flag will be checked in the
    test_kvm_cpu_feat() function and set or clear ECA_APIE accordingly.

    You can comment on this in the v3 patch.
    >

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