Philippe Mathieu-Daudé <[email protected]> writes:
> On 8/1/26 15:34, Alex Bennée wrote:
>> We tend to apply cpu_reset inconsistently throughout our various
>> models which leads to unintended ordering dependencies. This got in
>> the way in my last plugins series:
>> https://patchew.org/QEMU/[email protected]/
>> where I needed to shuffle things around to ensure that gdb register
>> creation was done after dependant peripherals had created their cpu
>> interfaces.
>> Regardless of that we do have a proper reset interface now and most
>> architectures have moved to it. This series attempts to clean-up the
>> remaining cases with proper qemu_register_reset() calls so reset is
>> called when we intend to.
>
> Last time I was blocked at this comment:
> https://lore.kernel.org/qemu-devel/[email protected]/
>From that:
--cpu_reset() <- brings cpu to known (after reset|poweron) state
cpu_common_realizefn()
if (dev->hotplugged) {
cpu_synchronize_post_init(cpu);
cpu_resume(cpu);
}
++cpu_reset() <-- looks to be too late, we already told hypervisor to run
undefined CPU, didn't we?
I would posit that the hotplug path is different as we online the CPU as
soon as its ready. Maybe that is just special cased as:
if (dev->hotplugged) {
cpu_reset(cpu);
cpu_synchronize_post_init(cpu);
cpu_resume(cpu);
}
Unless hotplug should also honour the reset tree in which case that
logic could be moved:
void cpu_reset(CPUState *cpu)
{
DeviceState *dev = DEVICE(cpu);
if (!dev->hotplugged) {
device_cold_reset(DEVICE(cpu));
} else {
/* hotplugging implies we should know how to setup */
cpu_synchronize_post_init(cpu);
}
trace_cpu_reset(cpu->cpu_index);
#ifdef CONFIG_TCG
/*
* Because vCPUs get "started" before the machine is ready we often
* can't provide all the information plugins need during
* cpu_common_initfn. However the vCPU will be reset a few times
* before we eventually set things going giving plugins an
* opportunity to update things.
*/
qemu_plugin_vcpu_reset_hook(cpu);
#endif
}
Do we have test cases for hotplugging CPUs?
>
>> Alex Bennée (12):
>> target/sh4: drop cpu_reset from realizefn
>> target/m68k: introduce env->reset_pc
>> hw/m68k: register a nextcube_cpu_reset handler
>> hw/m68k: register a mcf5208evb_cpu_reset handler
>> hw/m68k: register a an5206_cpu_reset handler
>> hw/m68k: just use reset_pc for virt platform
>> target/m68k: drop cpu_reset on realizefn
>> hw/mips: defer finalising gcr_base until reset time
>> hw/mips: drop cpu_reset in mips_cpu_realizefn
>> target/tricore: move cpu_reset from tricore_cpu_realizefn
>> target/arm: remove extraneous cpu_reset from realizefn
>> include/hw: expand cpu_reset function docs
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
