Re: [PATCH V3 05/10] x86/entry: Pass irqentry_state_t by reference

Ira Weiny
2020-11-16T18:49:36Z

On Sun, Nov 15, 2020 at 07:58:52PM +0100, Thomas Gleixner wrote:
> Ira,
>
> On Fri, Nov 06 2020 at 15:29, ira weiny wrote:
>
> Subject prefix wants to 'entry:'. This changes generic code and the x86
> part is just required to fix the generic code change.

Sorry, yes that was carried incorrectly from earlier versions.

>
> > Currently struct irqentry_state_t only contains a single bool value
> > which makes passing it by value is reasonable. However, future patches
> > propose to add information to this struct, for example the PKRS
> > register/thread state.
> >
> > Adding information to irqentry_state_t makes passing by value less
> > efficient. Therefore, change the entry/exit calls to pass irq_state by
> > reference.
>
> The PKRS muck needs to add an u32 to that struct. So how is that a
> problem?

There are more fields to be added for the kmap/pmem support. So this will be
needed eventually. Even though it is not strictly necessary in the next patch.

>
> The resulting struct still fits into 64bit which is by far more
> efficiently passed by value than by reference. So which problem are you
> solving here?

I'm getting ahead of myself a bit. I will be adding more fields for the
kmap/pmem tracking.

Would you accept just a clean up for the variable names in this patch? I could
then add the pass by reference when I add the new fields later. Or would an
update to the commit message be ok to land this now?

Ira

>
> Thanks
>
> tglx
>