Re: [PATCH v12 3/3] KVM: s390: resetting the Topology-Change-Report

From: Pierre Morel
Date: Thu Jul 14 2022 - 04:32:50 EST

On 7/13/22 11:01, Janosch Frank wrote:
On 7/12/22 13:17, Pierre Morel wrote:

On 7/12/22 10:47, Janis Schoetterl-Glausch wrote:
On 7/12/22 09:24, Pierre Morel wrote:



In userland we check any wrong selector before the instruction goes back
to the guest.

I opt for passing the lower selectors down for QEMU to handle.


But that's only relevant if STSI can be extended without a capability, which is why I asked about that.

Logicaly any change, extension, in the architecture should be signaled
by a facility bit or something.

Even testing the facility or PV in the kernel is for my opinion arguable in the case we do not do any treatment in the kernel.

That's actually a good point.

New instruction interceptions for PV will need to be enabled by KVM via a switch somewhere since the UV can't rely on the fact that KVM will correctly handle it without an enablement.

So please remove the pv check



    +static int kvm_s390_set_topology(struct kvm *kvm, struct kvm_device_attr *attr)

kvm_s390_set_topology_changed maybe?
kvm_s390_get_topology_changed below then.


It's long but it's rarely used.
Maybe shorten topology to "topo"

I use



Pierre Morel
IBM Lab Boeblingen