Re: [Xen-devel] [PATCH] gic:vgic: avoid excessive conversions

[Andrii Anisov <andrii.anisov@xxxxxxxxx>]

On 19.11.18 15:54, Julien Grall wrote:
> You didn't get my point. You removed a parameter without explaining 
> why it is fine.
It is a pure optimization. If you look through the code, you can see 
that callers of these functions already have a correspondent `struct 
pending_irq` pointer. But they pass irq number (and priority) to 
gic_raise_guest_irq/gic_raise_inflight_irq so that they should calculate 
the pointer again, what is suboptimal.

> In that context, the caller for LPI is using lpi_priority.
What in its turn is not taken into consideration by the current 
`gic_raise_guest_irq` function implementation. Even clearly ignored, 
because the priority abstraction is only needed by 
`gic_add_to_lr_pending` to insert a pending irq into `lr_queue`, but it 
does ordering by `p->priority` only.
> With your change, it is becoming issue with the interface because it 
> may not pass the correct things.
Now the interface of `gic_raise_guest_irq` function corresponds to its 
implementation in addition to optimization.

> So this not a cleanup and there must be a reason why lpi_priority was 
> passed instead of priority.
Moreover, if one would like or plan to honor lpi_priority in 
`gic_raise_guest_irq`, he can freely extract it from a pending_irq 
structure. It is still there.

--

Sincerely,
Andrii Anisov.


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