Yes, the value of the cpu_index seems to track the number of clone() syscalls. (I did strace the process, but forgot to look for clone() syscalls... I still have vfork()/execve() on the brain.) ________________________________ From: Qemu-discuss <qemu-discuss-bounces+robhenry=microsoft....@nongnu.org> on behalf of Philippe Mathieu-Daudé <f4...@amsat.org> Sent: Sunday, September 19, 2021 10:54 AM To: rrh.henry <rrh.he...@gmail.com>; qemu-disc...@nongnu.org <qemu-disc...@nongnu.org> Cc: Alex Bennée <alex.ben...@linaro.org>; qemu-devel <qemu-devel@nongnu.org> Subject: [EXTERNAL] Re: Range of vcpu_index to plugin callbacks
(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.
