linux-kernel - Re: [PATCH v4 0/5] initialize SCTRL2

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Message-ID: <aL7QySSGoI5p0B70@e133380.arm.com>
Date: Mon, 8 Sep 2025 13:49:13 +0100
From: Dave Martin <Dave.Martin@....com>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: catalin.marinas@....com, will@...nel.org, broonie@...nel.org,
	oliver.upton@...ux.dev, anshuman.khandual@....com, robh@...nel.org,
	james.morse@....com, mark.rutland@....com, joey.gouly@....com,
	ahmed.genidi@....com, kevin.brodsky@....com,
	scott@...amperecomputing.com, mbenes@...e.cz,
	james.clark@...aro.org, frederic@...nel.org, rafael@...nel.org,
	pavel@...nel.org, ryan.roberts@....com, suzuki.poulose@....com,
	maz@...nel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	kvmarm@...ts.linux.dev
Subject: Re: [PATCH v4 0/5] initialize SCTRL2_ELx

Hi,

On Mon, Sep 08, 2025 at 12:22:34PM +0100, Yeoreum Yun wrote:
> Hi,
> 
> > [...]
> >
> > > > > > Have you tested all the code paths, or are there some things that have
> > > > > > not been tested?
> > > > >
> > > > > I've tested for pKVM, nested and nhve and crash path
> > > > > (I do my best what can I do for modified path).
> > > >
> > > > Was that just confirming that the kernel boots / does not crash?
> > >
> > > Not only that, since the my last mistake, I've check it with debugger
> > > too -- set the SCTLR2_ELx as I expected.
> > >
> > > >
> > > > What about CPU suspend/resume and hotplug?
> > >
> > > Of course It's done both enter/exit idle and hotplug with related kselftest test.
> >
> > Were you able to step through these paths, too?
> 
> Yes. with debugger and some trick with:
>   asm volatile("b ." ::: "memory");
> 
> checking a cpu idle (by not loading any work) without any load and
> checking cpu-hotplug with kselftest's cpu-on-off-test.sh.
> 
> So, by hitting the "b .", I've stepped in and confirm the SCTLR2_ELx set
> as it intended.

OK, that sounds reasonable comprehensive.

[...]

> > Looking again through this series, I realised that the requirements for
> > this feature are not documented in booting.rst.
> >
> > Does the following patch look good to you?  If so, feel free to append
> > it to the series (with your Reviewed-by, if you're happy with the
> > changes).
> >
> > It's probably worth double-checking the bit numbers etc.  I wrote this
> > some weeks ago and then forgot about it.
> 
> I've missed this and Thanks for your efforts.
> The bits you documented have no problem as far as I checked.
> Let me include this too in next series.
> 
> (I'm still checking your suggestion to use .ifc. as soon as finish
> this. I'll repost it according to your suggestion)
> 
> 
> Thanks!

OK, I'll take another look when you repost.

Cheers
---Dave