Re: [PATCH v8 00/20] Convert x86 & arm64 to use generic page walk

From: Steven Price <steven.price@arm.com>
To: Dave Hansen <dave.hansen@intel.com>,
	linux-mm@kvack.org,
	Linus Torvalds <torvalds@linux-foundation.org>
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, "Will Deacon" <will.deacon@arm.com>,
	linux-kernel@vger.kernel.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>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	linux-arm-kernel@lists.infradead.org, "Liang,
	Kan" <kan.liang@linux.intel.com>
Subject: Re: [PATCH v8 00/20] Convert x86 & arm64 to use generic page walk
Date: Wed, 17 Apr 2019 15:28:54 +0100	[thread overview]
Message-ID: <3acbf061-8c97-55eb-f4b6-163a33ea4d73@arm.com> (raw)
In-Reply-To: <3b9561d0-3bde-ef7a-0313-c2cc6216f94d@intel.com>

On 12/04/2019 15:44, Dave Hansen wrote:
> On 4/10/19 7:56 AM, Steven Price wrote:
>> Gentle ping: who can take this? Is there anything blocking this series?
> 
> First of all, I really appreciate that you tried this.  Every open-coded
> page walk has a set of common pitfalls, but is pretty unbounded in what
> kinds of bugs it can contain.  I think this at least gets us to the
> point where some of those pitfalls won't happen.  That's cool, but I'm a
> worried that it hasn't gotten easier in the end.

My plan was to implement the generic infrastructure and then work to
remove the per-arch code for ptdump debugfs where possible. This patch
series doesn't actually get that far because I wanted to get some
confidence that the general approach would be accepted.

> Linus also had some strong opinions in the past on how page walks should
> be written.  He needs to have a look before we go much further.

Fair enough. I'll post the initial work I've done on unifying the
x86/arm64 ptdump code - the diffstat is a bit nicer on that - but
there's still work to be done so I'm posting just as an RFC.

Thanks,

Steve