On 5/28/21 5:50 PM, Anchal Agarwal wrote:

That only fails during boot but not after the control jumps into the image. The
non boot cpus are brought offline(freeze_secondary_cpus) and then online via cpu hotplug path. In that case xen_vcpu_setup doesn't invokes the hypercall again.

OK, that makes sense --- by that time VCPUs have already been registered. What I don't understand though is why resume doesn't fail every time --- xen_vcpu and xen_vcpu_info should be different practically always, shouldn't they? Do you observe successful resumes when the hypercall fails?

Another line of thought is something what kexec does to come around this problem
is to abuse soft_reset and issue it during syscore_resume or may be before the image get loaded.
I haven't experimented with that yet as I am assuming there has to be a way to re-register vcpus during resume.

Right, that sounds like it should work.


-boris