On 12/5/18 11:07 AM, Collin Walling wrote:
> On 12/5/18 4:02 AM, David Hildenbrand wrote:
>> On 04.12.18 23:06, Collin Walling wrote:
>>> Diagnose 318 is a privileged instruction that must be interpreted by
>>> SIE and handled via KVM.
>>>
>>> The control program name and version codes (CPNC and CPVC) set by this
>>> instruction are saved to the kvm->arch struct. The CPNC is also set in
>>> the SIE control block of all VCPUs. The new kvm_s390_set_misc interface
>>> is introduced for migration.
>>>
>>> Signed-off-by: Collin Walling <walling@xxxxxxxxxxxxx>
>>> Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
>>> ---
[...]
>>>
>>> +void kvm_s390_set_cpc(struct kvm *kvm, u64 cpc)
>>> +{
>>> + struct kvm_vcpu *vcpu;
>>> + int i;
>>> +
>>> + mutex_lock(&kvm->lock);
>>> + kvm->arch.diag318_info.cpc = cpc;
>>> +
>>> + VM_EVENT(kvm, 3, "SET: cpnc: 0x%x cpvc: 0x%llx",
>>> + (u8)kvm->arch.diag318_info.cpnc, (u64)kvm->arch.diag318_info.cpvc);
>>> +
>>> + kvm_for_each_vcpu(i, vcpu, kvm) {
>>> + vcpu->arch.sie_block->cpnc = kvm->arch.diag318_info.cpnc;
>>
>> No, that does not look completely right. The other VCPUs could be
>> running in the SIE. Can you update that via a sync request instead?
>>
>> (after a VCPU updated the CPNC, other VCPUS could read for some time the
>> old value, as values in this part of the sie_block might be cached while
>> a CPU is in the SIE)
>>
>
> True. There are different name codes for other control programs (v/ZM, z/OS, etc).
> We should make sure that the name code is properly updated for all VCPUs if we are
> running a non-linux environment on top of KVM.
>
> Thanks for the heads up!
>
I've been reading up on what the other requests (KVM_REQ_*) are used for, and none of them
seem to make sense for what we want to do here (update a field in the vcpu). So let's see
if I fully understand how this should be implemented:
1) create a new s390 specific request that will handle updating the cpc
2) call a sync_broadcast using the new request within set_cpc
Alternatively, I think a vcpu block would work as well (you mentioned this in the RFC back
at the end of August / beginning of September).
Am I headed in the right direction?
[...]
--
Respectfully,
- Collin Walling
