[Qemu-devel] QEMU + KVM PSCI and VCPU creation / destruction

[Claudio Fontana]

Hello,

while heavily testing PSCI on QEMU+KVM during OSv enablement, I encountered, 
among others, the following issue:

I am running a test in which I boot an OS at EL1 under KVM, then boot a 
secondary VCPU,
then immediately call PSCI for a SYSTEM_RESET (reboot).

This loops over infinitely, or, as a matter of fact, until I run out of memory 
in the Foundation Model.

Now, before submitting another support request for the Model, I checked the 
code for the handling of PSCI, and it turns out that KVM handles the HVC and 
then sets an exit reason for QEMU to check,
which again sets the system_reset_requested to true, which causes a 
qemu_system_reset.

Now in there I see the call to qemu_devices_reset() and 
cpu_synchronize_all_post_reset(),
but are actually the VCPU destroyed? Is the VM destroyed? Or are new resources 
allocated at the next boot whenever PSCI asks for another VCPU to be booted via 
KVM_CREATE_VCPU etc?

If the resources associated to the VCPU (and VM?) are not freed, isn't this 
always going to cause leak in the host?

After around 3 hours of continuous PSCI secondary boot followed by SYSTEM_RESET 
I run out of memory on the host.

Thanks,

Claudio