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Date: Tue, 8 Apr 2014 18:12:03 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Mel Gorman <mgorman@suse.de>,
        Linux-X86 <x86@kernel.org>, Cyrill Gorcunov <gorcunov@gmail.com>,
        Ingo Molnar <mingo@kernel.org>, Steven Noonan <steven@uplinklabs.net>,
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        Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
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Subject: Re: [RFC PATCH 0/5] Use an alternative to _PAGE_PROTNONE for
 _PAGE_NUMA v2
Message-ID: <20140408161203.GQ10526@twins.programming.kicks-ass.net>
References: <1396962570-18762-1-git-send-email-mgorman@suse.de>
 <53440A5D.6050301@zytor.com>
 <CA+55aFwc6Jdf+As9RJ3wJWuOGEGmiaYWNa-jp2aCb9=ZiiqV+A@mail.gmail.com>
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On Tue, Apr 08, 2014 at 08:22:15AM -0700, Linus Torvalds wrote:
> On Tue, Apr 8, 2014 at 7:40 AM, H. Peter Anvin <hpa@zytor.com> wrote:
> >
> > David, is your patchset going to be pushed in this merge window as expected?
> 
> Apparently aiming for 3.16 right now.
> 
> > That being said, these bits are precious, and if this ends up being a
> > case where "only Xen needs another bit" once again then Xen should
> > expect to get kicked to the curb at a moment's notice.
> 
> Quite frankly, I don't think it's a Xen-only issue. The code was hard
> to figure out even without the Xen issues. For example, nobody ever
> explained to me why it
> 
>  (a) could be the same as PROTNONE on x86
>  (b) could not be the same as PROTNONE in general
> 
> I think the best explanation for it so far was from the little voices
> in my head that sang "It's a kind of Magic", and that isn't even
> remotely the best song by Queen.

Right; so initially when I started doing the numa scanning thing I
implemented b. I've never quite understood why that wasn't chosen; but
since Mel already got the PAGE_NUMA bits merged by the time I
re-surfaced, I didn't want to argue too much about it.