Re: [PATCH 1/4] hw/nvme: avoid unnecessary call to irq (de)assertion functions

[Stefan Hajnoczi]

On Thu, 11 Aug 2022 at 11:38, Jinhao Fan <fanjinhao21s@ict.ac.cn> wrote:
>
> nvme_irq_assert() only does useful work when cq->irq_enabled is true.
> nvme_irq_deassert() only works for pin-based interrupts. Avoid calls
> into these functions if we are sure they will not do useful work.
>
> This will be most useful when we use eventfd to send interrupts. We
> can avoid the unnecessary overhead of signalling eventfd.
>
> Signed-off-by: Jinhao Fan <fanjinhao21s@ict.ac.cn>
> ---
>  hw/nvme/ctrl.c | 40 ++++++++++++++++++++++------------------
>  1 file changed, 22 insertions(+), 18 deletions(-)

There is code duplication and nvme_irq_assert/deassert() check
->irq_enabled and msix_enabled() again.

Can the logic be moved into assert()/deassert() so callers don't need
to duplicate the checks?

(I assume the optimization is that eventfd syscalls are avoided, not
that the function call is avoided.)

Stefan