From: Pierre Morel <pmorel@linux.vnet.ibm.com>
To: Tony Krowiak <akrowiak@linux.vnet.ibm.com>,
Halil Pasic <pasic@linux.vnet.ibm.com>,
linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org
Cc: freude@de.ibm.com, schwidefsky@de.ibm.com,
heiko.carstens@de.ibm.com, borntraeger@de.ibm.com,
cohuck@redhat.com, kwankhede@nvidia.com,
bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com,
alex.williamson@redhat.com, alifm@linux.vnet.ibm.com,
mjrosato@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com,
thuth@redhat.com, berrange@redhat.com, fiuczy@linux.vnet.ibm.com,
buendgen@de.ibm.com
Subject: Re: [PATCH v3 04/14] KVM: s390: device attribute to set AP interpretive execution
Date: Thu, 15 Mar 2018 16:45:35 +0100 [thread overview]
Message-ID: <5ed8017b-0168-9a50-234b-cfe9258eab72@linux.vnet.ibm.com> (raw)
In-Reply-To: <46a7e838-2be2-9587-6eb2-3bba95485609@linux.vnet.ibm.com>
On 15/03/2018 16:26, Tony Krowiak wrote:
> On 03/15/2018 09:00 AM, Pierre Morel wrote:
>> On 14/03/2018 22:57, Halil Pasic wrote:
>>>
>>> On 03/14/2018 07:25 PM, Tony Krowiak wrote:
>>>> The VFIO AP device model exploits interpretive execution of AP
>>>> instructions (APIE) to provide guests passthrough access to AP
>>>> devices. This patch introduces a new device attribute in the
>>>> KVM_S390_VM_CRYPTO device attribute group to set APIE from
>>>> the VFIO AP device defined on the guest.
>>>>
>>>> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
>>>> ---
>>> [..]
>>>
>>>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>>>> index a60c45b..bc46b67 100644
>>>> --- a/arch/s390/kvm/kvm-s390.c
>>>> +++ b/arch/s390/kvm/kvm-s390.c
>>>> @@ -815,6 +815,19 @@ static int kvm_s390_vm_set_crypto(struct kvm
>>>> *kvm, struct kvm_device_attr *attr)
>>>> sizeof(kvm->arch.crypto.crycb->dea_wrapping_key_mask));
>>>> VM_EVENT(kvm, 3, "%s", "DISABLE: DEA keywrapping support");
>>>> break;
>>>> + case KVM_S390_VM_CRYPTO_INTERPRET_AP:
>>>> + if (attr->addr) {
>>>> + if (!test_kvm_cpu_feat(kvm, KVM_S390_VM_CPU_FEAT_AP))
>>> Unlock mutex before returning?
>>>
>>> Maybe flip conditions (don't allow manipulating apie if feature not
>>> there).
>>> Clearing the anyways clear apie if feature not there ain't too bad, but
>>> rejecting the operation appears nicer to me.
>>>
>>>> + return -EOPNOTSUPP;
>>>> + kvm->arch.crypto.apie = 1;
>>>> + VM_EVENT(kvm, 3, "%s",
>>>> + "ENABLE: AP interpretive execution");
>>>> + } else {
>>>> + kvm->arch.crypto.apie = 0;
>>>> + VM_EVENT(kvm, 3, "%s",
>>>> + "DISABLE: AP interpretive execution");
>>>> + }
>>>> + break;
>>>> default:
>>>> mutex_unlock(&kvm->lock);
>>>> return -ENXIO;
>>> I wonder how the loop after this switch works for
>>> KVM_S390_VM_CRYPTO_INTERPRET_AP:
>>>
>>> kvm_for_each_vcpu(i, vcpu, kvm) {
>>> kvm_s390_vcpu_crypto_setup(vcpu);
>>> exit_sie(vcpu);
>>> }
>>>
>>> From not doing something like for KVM_S390_VM_CRYPTO_INTERPRET_AP
>>>
>>> if (kvm->created_vcpus) {
>>> mutex_unlock(&kvm->lock);
>>> return -EBUSY;
>>> and from the aforementioned loop I guess ECA.28 can be changed
>>> for a running guest.
>>>
>>> If there are running vcpus when KVM_S390_VM_CRYPTO_INTERPRET_AP is
>>> changed (set) these will be taken out of SIE by exit_sie(). Then for
>>> the
>>> corresponding threads the control probably goes to QEMU (the
>>> emulator in
>>> the userspace). And it puts that vcpu back into the SIE, and then that
>>> cpu starts acting according to the new ECA.28 value. While other vcpus
>>> may still work with the old value of ECA.28.
>>>
>>> I'm not saying what I describe above is necessarily something broken.
>>> But I would like to have it explained, why is it OK -- provided I
>>> did not
>>> make any errors in my reasoning (assumptions included).
>>>
>>> Can you help me understand this code?
>>>
>>> Regards,
>>> Halil
>>>
>>> [..]
>>>
>>
>> I have the same concerns as Halil.
>>
>> We do not need to change the virtulization type
>> (hardware/software) on the fly for the current use case.
>>
>> Couldn't we delay this until we have one and in between only make the
>> vCPU hotplug clean?
>>
>> We only need to let the door open for the day we have such a use case.
> Are you suggesting this code be removed? If so, then where and under
> what conditions would
> you suggest setting ECA.28 given you objected to setting it based on
> whether the
> AP feature is installed?
I would only call kvm_s390_vcpu_crypto_setup() from inside
kvm_arch_vcpu_init()
as it is already.
>>
>>
>> Pierre
>>
>>
>>
>
--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany
next prev parent reply other threads:[~2018-03-15 15:45 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-14 18:25 [PATCH v3 00/14] s390: vfio-ap: guest dedicated crypto adapters Tony Krowiak
2018-03-14 18:25 ` [PATCH v3 01/14] KVM: s390: refactor crypto initialization Tony Krowiak
2018-03-15 12:26 ` Pierre Morel
2018-03-15 14:48 ` Tony Krowiak
2018-03-15 14:55 ` Pierre Morel
2018-03-26 8:44 ` Cornelia Huck
2018-03-29 18:57 ` Tony Krowiak
2018-04-03 11:26 ` Cornelia Huck
2018-04-05 10:42 ` Christian Borntraeger
2018-04-05 10:45 ` Christian Borntraeger
2018-04-05 13:16 ` Tony Krowiak
2018-03-14 18:25 ` [PATCH v3 02/14] s390: zcrypt: externalize AP instructions available function Tony Krowiak
2018-03-14 18:25 ` [PATCH v3 03/14] KVM: s390: CPU model support for AP virtualization Tony Krowiak
2018-03-27 10:59 ` Cornelia Huck
2018-03-27 11:22 ` Pierre Morel
2018-03-27 11:30 ` Cornelia Huck
2018-03-14 18:25 ` [PATCH v3 04/14] KVM: s390: device attribute to set AP interpretive execution Tony Krowiak
2018-03-14 21:57 ` Halil Pasic
2018-03-15 13:00 ` Pierre Morel
2018-03-15 15:26 ` Tony Krowiak
2018-03-15 15:45 ` Pierre Morel [this message]
2018-03-15 17:21 ` Tony Krowiak
2018-03-15 17:56 ` Pierre Morel
2018-03-15 23:39 ` Tony Krowiak
2018-03-16 7:51 ` Pierre Morel
2018-03-16 16:09 ` Tony Krowiak
2018-03-20 17:58 ` Tony Krowiak
2018-03-20 22:48 ` Halil Pasic
2018-04-02 18:55 ` Tony Krowiak
2018-03-15 15:23 ` Tony Krowiak
2018-03-15 16:00 ` Pierre Morel
2018-03-15 23:37 ` Tony Krowiak
2018-03-15 16:25 ` Halil Pasic
2018-03-14 18:25 ` [PATCH v3 05/14] s390: vfio-ap: base implementation of VFIO AP device driver Tony Krowiak
2018-03-15 13:25 ` Pierre Morel
2018-03-15 17:25 ` Tony Krowiak
2018-03-27 11:17 ` Cornelia Huck
2018-03-27 14:45 ` Pierre Morel
2018-04-03 9:56 ` Cornelia Huck
2018-04-03 10:57 ` Cornelia Huck
2018-04-03 13:02 ` Tony Krowiak
2018-03-14 18:25 ` [PATCH v3 06/14] s390: vfio-ap: register matrix device with VFIO mdev framework Tony Krowiak
2018-03-14 18:25 ` [PATCH v3 07/14] KVM: s390: interfaces to configure/deconfigure guest's AP matrix Tony Krowiak
2018-04-03 11:07 ` Cornelia Huck
2018-04-03 13:17 ` Tony Krowiak
2018-04-03 13:38 ` Cornelia Huck
2018-03-14 18:25 ` [PATCH v3 08/14] s390: vfio-ap: sysfs interfaces to configure adapters Tony Krowiak
2018-04-03 11:10 ` Cornelia Huck
2018-04-03 13:33 ` Tony Krowiak
2018-03-14 18:25 ` [PATCH v3 09/14] s390: vfio-ap: sysfs interfaces to configure domains Tony Krowiak
2018-04-03 11:17 ` Cornelia Huck
[not found] ` <1860430c-df59-6d58-77f9-b36c51595b4b@linux.vnet.ibm.com>
2018-04-03 15:19 ` Cornelia Huck
2018-04-03 15:42 ` Tony Krowiak
2018-03-14 18:25 ` [PATCH v3 10/14] s390: vfio-ap: sysfs interfaces to configure control domains Tony Krowiak
2018-03-14 18:25 ` [PATCH v3 11/14] s390: vfio-ap: sysfs interface to view matrix mdev matrix Tony Krowiak
2018-03-15 9:42 ` Pierre Morel
2018-03-15 14:52 ` Tony Krowiak
2018-03-15 15:35 ` Pierre Morel
2018-03-27 11:19 ` Cornelia Huck
2018-03-14 18:25 ` [PATCH v3 12/14] KVM: s390: configure the guest's AP devices Tony Krowiak
2018-03-14 18:25 ` [PATCH v3 13/14] s390: vfio-ap: implement VFIO_DEVICE_GET_INFO ioctl Tony Krowiak
2018-03-14 18:25 ` [PATCH v3 14/14] s390: doc: detailed specifications for AP virtualization Tony Krowiak
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