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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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