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Subject: Re: [PATCH v8 00/20] Convert x86 & arm64 to use generic page walk
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,
        =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= <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>
References: <20190403141627.11664-1-steven.price@arm.com>
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 <3b9561d0-3bde-ef7a-0313-c2cc6216f94d@intel.com>
From:   Steven Price <steven.price@arm.com>
Message-ID: <3acbf061-8c97-55eb-f4b6-163a33ea4d73@arm.com>
Date:   Wed, 17 Apr 2019 15:28:54 +0100
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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