Re: [PATCH v9 00/21] Generic page walk and ptdump

From: Thomas Gleixner
Date: Wed Jul 24 2019 - 10:38:03 EST

On Wed, 24 Jul 2019, Steven Price wrote:
> On 24/07/2019 14:57, Thomas Gleixner wrote:
> > From your 14/N changelog:
> >
> >> This keeps the output shorter and will help with a future change
> >
> > I don't care about shorter at all. It's debug information.
> Sorry, the "shorter" part was because Dave Hansen originally said[1]:
> > I think I'd actually be OK with the holes just not showing up. I
> > actually find it kinda hard to read sometimes with the holes in there.
> > I'd be curious what others think though.

I missed that otherwise I'd have disagreed right away.

> > I really do not understand why you think that WE no longer care about the
> > level (and the size) of the holes. I assume that WE is pluralis majestatis
> > and not meant to reflect the opinion of you and everyone else.
> Again, I apologise - that was sloppy wording in the commit message. By
> "we" I meant the code not any particular person.

Nothing to apologize. Common mistake of trying to impersonate code. That
always reads wrong :)

> > I have no idea whether you ever had to do serious work with PT dump, but I
> > surely have at various occasions including the PTI mess and I definitely
> > found the size and the level information from holes very useful.
> On arm64 we don't have those lines, but equally it's possible they might
> be useful in the future. So this might be something to add.
> As I said in a previous email[3] I was dropping the lines from the
> output assuming nobody had any objections. Since you find these lines
> useful, I'll see about reworking the change to retain the lines.

That would be great and as I saw in the other mail, Mark wants to have them
as well :)

That reminds me, that I had a patch when dealing with L1TF which printed
the PFNs so I could verify that the mitigations do what they are supposed
to do, but that patch got obviously lost somewhere down the road.