Re: [PATCH v2 2/3] KVM: selftests: Extend @shape to allow creation of VM without in-kernel APIC

[Sean Christopherson <seanjc@google.com>]

On Mon, Apr 01, 2024, Manali Shukla wrote:
> Currently, all the VMs are created with in-kernel APIC support in KVM
> selftests because KVM_CREATE_IRQCHIP ioctl is called by default from
> kvm_arch_vm_post_create().
> 
> Carve out space in the @shape passed to the various VM creation helpers to
> allow using the shape to control creation of a VM without in-kernel APIC
> support or with in-kernel APIC support.
> 
> This is a preparatory patch to create a vm without in-kernel APIC support for
> the KVM_X86_DISABLE_EXITS_HLT test.

Ugh, when I suggested creating a VM without an in-kernel APIC as away to easily
test that HLT doesn't exit, I wasn't thinking about the side effects of creating
a runnable VM without an in-kernel APIC.  The other downside is that practically
no one uses a userspace local APIC these days, i.e. the selftest isn't a great
representation of real world setups.

Given that KVM already provides vcpu->stat.halt_exits, using a stats FD for
verifying exiting behavior is probably a better option.  The other check that
could be added would be to verify that mp_state is always RUNNABLE (which is a
bug/gap in KVM as migrating a vCPU that was halted in the guest won't resume in
a halted state on the target).