Re: [PATCH 11/16] accel/kvm: Consistently return CPU halt state from process_async_events

["Philippe Mathieu-Daudé" <philmd@oss.qualcomm.com>]

On 18/8/26 12:30, Paolo Bonzini wrote:
> On Tue, Aug 18, 2026 at 11:24 AM Philippe Mathieu-Daudé
> <philmd@oss.qualcomm.com> wrote:
>>> Your patch is correct because, even if cpu_thread_is_idle() sees cpu-
>>>   >halted == false, the flag could become true during
>>> process_queued_cpu_work() because it releases the BQL.
>>>
>>> However, I think the better fix is to remove the return code, and check
>>> cpu->halted in kvm_cpu_exec().
>>
>> Looking at it, even better would be to move *process_async_events()
>> from inner loop to outer loop for all accelerators. For HW accels it
>> seems quite trivial; for TCG I need to figure if it is safe to call
>> icount_prepare_for_run() with the BQL taken, due to the replay_mutex
>> uses -- here the win is cpu_handle_halt() ends restricted to system
>> and we can remove the odd EXCP_HLT handling in user emulation.
> 
> Makes sense, but probably it would be a series of its own. :)

Good, right.

(FYI the motivation behind these cleanups and documentation is to
get hybrid-acceleration, so a consistent vcpu_thread_routine between
accelerators:
https://lore.kernel.org/qemu-devel/20250620172751.94231-10-philmd@linaro.org/)