Re: MSI interrupts

On Wed, 19 Mar 2025 15:20:20 +0000, Stefan Monnier wrote:

MitchAlsup1 [2025-03-17 21:49:18] wrote:

On Mon, 17 Mar 2025 18:33:09 +0000, EricP wrote:

Method 1 is simplest, it injects the interrupt request at Retire
as that's where the state of everything is synchronized.

[...]

Lowest interrupt Latency
Highest waste of power (i.e., work)
>

Method 2 pipelines the switch by injecting the interrupt request at
Fetch.

[...]

Interrupt latency is dependent on executing instructions,
Lowest waste of power

>
What do existing CPUs do?

Lean in the direction of method 2 will fallback position of method 1
if anything goes wrong.

Method 2 looks insanely messy, so I'd assume method 1 is the standard
approach, right?

It is "not that bad" on the large scale of things.

>
        Stefan