>>> On 19.09.18 at 13:11, <[email protected]> wrote: > The scenario is that we are trying to query the state of a VCPU (please > note: just query). That means that we're only interested in getting some > coherent VCPU state via the XEN_DOMCTL_gethvmcontext_partial domctl. > > We don't care if said state ends up being saved for the migration stream > or not, so in that respect the answer to Roger's question is: no size > increase or difference whatsoever.
"We don't care" is too little. _We_ care that state for offline vCPU-s does not make it into the migration stream. And at this point I think you mean "no size increase or difference whatsoever _intended_", since removing the check in question would result in a size increase afaict. > All we want to do is to be able to query the state of any VCPU in the > valid range of VCPUs assigned to the domain, online or not. We believe > being able to query them is reasonable, and the SDM states that they do > have a state (whatever it happens to be: the init state, after reset, etc.). I didn't know the SDM stated anything about offline vCPU-s. There's (according to my way of looking at things) no bare hardware equivalent to this state, which means whatever the SDM says is not applicable. > For example, please look at this XenServer-only patch: > > https://github.com/xenserver/xen.pg/blob/XS-7.1.x/master/x86-domctl-Don-t-pa > use-the-whole-domain-if-only-gett.patch That's what iirc Alexandru's series started from. > Now about the "the agent should do something else if the VCPU is down" > objection, that's not possible with the current Xen code: -ENOENT is > returned both when the VCPU is down _and_ when the VCPU index is out of > bounds (so if I query the state of VCPU 10 on a 2-VCPUs guest). If there are no other ways to inquire vCPU state, I'm sure we can provide some. I also don't view disambiguating the error code as an impossible thing to do. Jan _______________________________________________ Xen-devel mailing list [email protected] https://lists.xenproject.org/mailman/listinfo/xen-devel
