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

From: Thomas Gleixner <tglx@linutronix.de>
To: Steven Price <steven.price@arm.com>
Cc: "Mark Rutland" <mark.rutland@arm.com>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Andy Lutomirski" <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"James Morse" <james.morse@arm.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Will Deacon" <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org, "Liang,
	Kan" <kan.liang@linux.intel.com>
Subject: Re: [PATCH v9 00/21] Generic page walk and ptdump
Date: Wed, 24 Jul 2019 16:37:53 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1907241620140.1791@nanos.tec.linutronix.de> (raw)
In-Reply-To: <fd898367-b44e-9328-bdab-7a3de0db6bda@arm.com>

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.

Thanks,

	tglx