Re: [PATCH v3 1/8] serial: fake IRQ-regs context in poll handlers

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 05/02/2024 13:27, Jan Beulich wrote:
> In preparation of dropping the register parameters from
> serial_[rt]x_interrupt() and in turn from IRQ handler functions,
> register state needs making available another way for the few key
> handlers which need it. Fake IRQ-like state.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> The use of guest_cpu_user_regs() in dbc_uart_poll() is inconsistent with
> other console poll functions we have, and it's unclear whether that's
> actually generally correct.
Is it? Looking at ns16550_poll() we would pass guest_user_regs() if 
run_in_exception() doesn't exist. But looking at the caller, no-on seems 
to care about the 'regs'. So is this just a latent bug?
BTW, do you have an idea why the poll function is not run in an 
exception handler?
> Andrew suggested to move set_irq_regs() to BUGFRAME_run_fn handling;
> it's not clear to me whether that would be (a) correct from an abstract
> pov (that's exception, not interrupt context after all) 
I agree with that.

> and (b) really beneficial.
I guess this could help to reduce the amount of churn. I can't really 
make my mind whether this is worth it or not. So I would keep it as you did.
Cheers,

--
Julien Grall