On Fri, 29 Aug 2025 17:31:09 +0200
Paolo Bonzini <pbonz...@redhat.com> wrote:
> Right now, cpu_exit() is not usable from all accelerators because it
> includes a TCG-specific thread kick. In fact, cpu_exit() doubles as
> the TCG thread-kick via tcg_kick_vcpu_thread().
>
> In preparation for changing that, inline cpu_exit() into
> tcg_kick_vcpu_thread(). The direction of the calls can then be
> reversed, with an accelerator-independent cpu_exit() calling into
> qemu_vcpu_kick() rather than the opposite.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
Reviewed-by: Igor Mammedov <imamm...@redhat.com>
> ---
> accel/tcg/cpu-exec.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index 9241bcadb5f..3ae545e888f 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
> @@ -751,7 +751,16 @@ static inline bool cpu_handle_exception(CPUState *cpu,
> int *ret)
>
> void tcg_kick_vcpu_thread(CPUState *cpu)
> {
> - cpu_exit(cpu);
> + /*
> + * Ensure cpu_exec will see the reason why the exit request was set.
> + * FIXME: this is not always needed. Other accelerators instead
> + * read interrupt_request and set exit_request on demand from the
> + * CPU thread; see kvm_arch_pre_run() for example.
> + */
> + qatomic_store_release(&cpu->exit_request, true);
> +
> + /* Ensure cpu_exec will see the exit request after TCG has exited. */
> + qatomic_store_release(&cpu->neg.icount_decr.u16.high, -1);
> }
>
> static inline bool icount_exit_request(CPUState *cpu)
> @@ -780,7 +789,8 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
> /* Clear the interrupt flag now since we're processing
> * cpu->interrupt_request and cpu->exit_request.
> * Ensure zeroing happens before reading cpu->exit_request or
> - * cpu->interrupt_request (see also smp_wmb in cpu_exit())
> + * cpu->interrupt_request (see also store-release in
> + * tcg_kick_vcpu_thread())
> */
> qatomic_set_mb(&cpu->neg.icount_decr.u16.high, 0);
>
