Re: Range of vcpu_index to plugin callbacks

[Philippe Mathieu-Daudé]

(Cc'ing qemu-devel@ mailing list since this is a development question).

On 9/19/21 19:44, Robert Henry wrote:
> What is the range of the values for vcpu_index given to callbacks, such as:
> 
> typedef void (*qemu_plugin_vcpu_udata_cb_t)(unsigned int vcpu_index,
> void *userdata);
> 
> Empirically, when QEMU is in system mode, the maximum vcpu_index is 1
> less than the -smp cpus=$(NCPUS) value.
> 
> Empirically, when QEMU is in user mode, the values for vcpu_index slowly
> increase without an apparent upper bound known statically (or when the
> plugin is loaded?).

Isn't it related to clone() calls? I'd expect new threads use
a new vCPU, incrementing vcpu_index. But that is just a guess
without having looked at the code to corroborate...

Regards,

Phil.