[PATCH/s390-next,3/3] s390x/flic: migrate ais states

Commit Message

Christian Borntraeger July 13, 2017, 1:58 p.m. UTC

On 07/13/2017 03:10 PM, Cornelia Huck wrote:
> On Thu, 13 Jul 2017 15:02:08 +0200
> Christian Borntraeger <[e-mail]> wrote:
> 
>> On 07/13/2017 02:27 PM, Cornelia Huck wrote:
>>> On Thu, 13 Jul 2017 12:40:29 +0200
>>> Christian Borntraeger <[e-mail]> wrote:
>>>   
>>>> From: Yi Min Zhao <[e-mail]>
>>>>
>>>> During migration we should transfer ais states to the target guest.
>>>> This patch introduces a subsection to kvm_s390_flic_vmstate and new
>>>> vmsd for qemu_flic. The ais states need to be migrated only when
>>>> ais is supported.
>>>>
>>>> Signed-off-by: Yi Min Zhao <[e-mail]>
>>>> Signed-off-by: Christian Borntraeger <[e-mail]>
>>>> ---
>>>>  hw/intc/s390_flic.c          | 20 ++++++++++++
>>>>  hw/intc/s390_flic_kvm.c      | 75 ++++++++++++++++++++++++++++++++++++++++++++
>>>>  include/hw/s390x/s390_flic.h |  1 +
>>>>  3 files changed, 96 insertions(+)
> 
>>>> +static int kvm_flic_ais_post_load(void *opaque, int version_id)
>>>> +{
>>>> +    KVMS390FLICStateMigTmp *tmp = opaque;
>>>> +    KVMS390FLICState *flic = tmp->parent;
>>>> +    struct kvm_s390_ais_all ais = {
>>>> +        .simm = tmp->simm,
>>>> +        .nimm = tmp->nimm,
>>>> +    };
>>>> +    struct kvm_device_attr attr = {
>>>> +        .group = KVM_DEV_FLIC_AISM_ALL,
>>>> +        .addr = (uint64_t)&ais,
>>>> +    };
>>>> +
>>>> +    if (!ais_needed(flic)) {
>>>> +        return -ENOSYS;
>>>> +    }  
>>>
>>> I do not understand this... does that mean that
>>> - we should never get here or 
>>> - we should not try to change the fields or
>>> - I need coffee?  
>>
>> My understanding is that this should not happen with a normal setup, 
>> but it can happen if the user does something "wrong". For example
>> use qemu without libvirt and with -cpu host (which is not migration safe)
>> and do a migration from a host that has AIS to a host that has no AIS.
>> In that case the target system will reject the migration (late, but hopefully
>> not too late).
> 
> A comment would be helpful here.

Something like

Comments

Cornelia Huck July 13, 2017, 2:01 p.m. UTC | #1

On Thu, 13 Jul 2017 15:58:30 +0200
Christian Borntraeger <[e-mail]> wrote:

> On 07/13/2017 03:10 PM, Cornelia Huck wrote:
> > On Thu, 13 Jul 2017 15:02:08 +0200
> > Christian Borntraeger <[e-mail]> wrote:
> >   
> >> On 07/13/2017 02:27 PM, Cornelia Huck wrote:  
> >>> On Thu, 13 Jul 2017 12:40:29 +0200
> >>> Christian Borntraeger <[e-mail]> wrote:
> >>>     
> >>>> From: Yi Min Zhao <[e-mail]>
> >>>>
> >>>> During migration we should transfer ais states to the target guest.
> >>>> This patch introduces a subsection to kvm_s390_flic_vmstate and new
> >>>> vmsd for qemu_flic. The ais states need to be migrated only when
> >>>> ais is supported.
> >>>>
> >>>> Signed-off-by: Yi Min Zhao <[e-mail]>
> >>>> Signed-off-by: Christian Borntraeger <[e-mail]>
> >>>> ---
> >>>>  hw/intc/s390_flic.c          | 20 ++++++++++++
> >>>>  hw/intc/s390_flic_kvm.c      | 75 ++++++++++++++++++++++++++++++++++++++++++++
> >>>>  include/hw/s390x/s390_flic.h |  1 +
> >>>>  3 files changed, 96 insertions(+)  
> >   
> >>>> +static int kvm_flic_ais_post_load(void *opaque, int version_id)
> >>>> +{
> >>>> +    KVMS390FLICStateMigTmp *tmp = opaque;
> >>>> +    KVMS390FLICState *flic = tmp->parent;
> >>>> +    struct kvm_s390_ais_all ais = {
> >>>> +        .simm = tmp->simm,
> >>>> +        .nimm = tmp->nimm,
> >>>> +    };
> >>>> +    struct kvm_device_attr attr = {
> >>>> +        .group = KVM_DEV_FLIC_AISM_ALL,
> >>>> +        .addr = (uint64_t)&ais,
> >>>> +    };
> >>>> +
> >>>> +    if (!ais_needed(flic)) {
> >>>> +        return -ENOSYS;
> >>>> +    }    
> >>>
> >>> I do not understand this... does that mean that
> >>> - we should never get here or 
> >>> - we should not try to change the fields or
> >>> - I need coffee?    
> >>
> >> My understanding is that this should not happen with a normal setup, 
> >> but it can happen if the user does something "wrong". For example
> >> use qemu without libvirt and with -cpu host (which is not migration safe)
> >> and do a migration from a host that has AIS to a host that has no AIS.
> >> In that case the target system will reject the migration (late, but hopefully
> >> not too late).  
> > 
> > A comment would be helpful here.  
> 
> Something like
> 
> diff --git a/hw/intc/s390_flic_kvm.c b/hw/intc/s390_flic_kvm.c
> index 4cf73ee..9b8dbd1 100644
> --- a/hw/intc/s390_flic_kvm.c
> +++ b/hw/intc/s390_flic_kvm.c
> @@ -452,6 +452,12 @@ static int kvm_flic_ais_post_load(void *opaque, int version_id)
>          .addr = (uint64_t)&ais,
>      };
>  
> +    /* This can happen when the user mis-configures its guests in an
> +     * incompatible fashion or without a CPU model. For example using
> +     * qemu with -cpu host (which is not migration safe) and do a
> +     * migration from a host that has AIS to a host that has no AIS.
> +     * In that case the target system will reject the migration here.
> +     */
>      if (!ais_needed(flic)) {
>          return -ENOSYS;
>      }

With that added:

Reviewed-by: Cornelia Huck <[e-mail]>

Patch

diff --git a/hw/intc/s390_flic_kvm.c b/hw/intc/s390_flic_kvm.c
index 4cf73ee..9b8dbd1 100644
--- a/hw/intc/s390_flic_kvm.c
+++ b/hw/intc/s390_flic_kvm.c
@@ -452,6 +452,12 @@  static int kvm_flic_ais_post_load(void *opaque, int version_id)
         .addr = (uint64_t)&ais,
     };
 
+    /* This can happen when the user mis-configures its guests in an
+     * incompatible fashion or without a CPU model. For example using
+     * qemu with -cpu host (which is not migration safe) and do a
+     * migration from a host that has AIS to a host that has no AIS.
+     * In that case the target system will reject the migration here.
+     */
     if (!ais_needed(flic)) {
         return -ENOSYS;
     }