Re: [PATCH] cmdline: document and enforce "extra_guest_irqs" upper bounds

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 04/04/2023 10:20, Jan Beulich wrote:
> PHYSDEVOP_pirq_eoi_gmfn_v<N> accepting just a single GFN implies that no
> more than 32k pIRQ-s can be used by a domain on x86. Document this upper
> bound.
>
> To also enforce the limit, (ab)use both arch_hwdom_irqs() (changing its
> parameter type) and setup_system_domains(). This is primarily to avoid
> exposing the two static variables or introducing yet further arch hooks.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> Instead of passing dom_xen into arch_hwdom_irqs(), NULL could also be
> used. That would make the connection to setup_system_domains() yet more
> weak, though.
>
> On Arm the upper limit right now effectively is zero, albeit with -
> afaict - no impact if a higher value was used (and hence permitting up
> to the default of 32 is okay albeit useless). The question though is
> whether the command line option as a whole shouldn't be x86-only.
AFAIK, ->nr_pirq is not used at all on Arm because we don't have any 
concept of PIRQs.
So I think it would be fine to move the command line option to x86-only 
(assuming this will not be needed on RISC-V).
Cheers,

--
Julien Grall