[PATCH 1/3] arm64: Use FEAT_HAFDBS to track dirty pages when available

[Chris Packham]

On Sat, 14 Oct 2023, 11:04 am Marc Zyngier, <maz at kernel.org> wrote:

> On 2023-10-13 03:40, Chris Packham wrote:
> > Hi Marc, Paul,
> >
> > On Sat, Mar 18, 2023 at 5:23 AM Ying-Chun Liu (PaulLiu)
> > <paul.liu at linaro.org> wrote:
> >>
> >> From: Marc Zyngier <maz at kernel.org>
> >>
> >> Some recent arm64 cores have a facility that allows the page
> >> table walker to track the dirty state of a page. This makes it
> >> really efficient to perform CMOs by VA as we only need to look
> >> at dirty pages.
> >>
> >> Signed-off-by: Marc Zyngier <maz at kernel.org>
> >> [ Paul: pick from the Android tree. Rebase to the upstream ]
> >> Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu at linaro.org>
> >> Cc: Tom Rini <trini at konsulko.com>
> >> Link:
> >>
> https://android.googlesource.com/platform/external/u-boot/+/3c433724e6f830a6b2edd5ec3d4a504794887263
> >
> > I think this may have caused a regression for the Marvell AC5X
> > board(s). I found that v2023.07 locked up at boot but v2023.01 was
> > fine. The lockup seemed to be in the 'Net:' init probably just as the
> > mvneta driver was being initialised.
> >
> > A git bisect led me to this change although for this specific change
> > instead of the lockup I get a crash so maybe I'm actually hitting a
> > different issue.
> >
> > Any thoughts as to why this may have caused problems?
>
> Not really. What CPUs does this platform have? What is the offending
> driver doing to trigger the issue? Can you provide some level of
> tracing?
>

The Marvell AC5X is a network switch ASIC with an integrated ARMv8 CPU (8.1
specifically I think).

I think there is something that the mvneta driver is doing triggering the
issue. I have another AC5X based board without an Ethernet port that boots
just fine (this is also why I didn't notice earlier).

I'll try and get some more debug out when I'm back in the office


>          M.
> --
> Jazz is not dead. It just smells funny...
>