linux-kernel - Re: [GIT PULL] x86/mm for 6.4

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Date:   Wed, 3 May 2023 21:01:47 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kirill.shutemov@...ux.intel.com
Subject: Re: [GIT PULL] x86/mm for 6.4

On Wed, May 03, 2023 at 10:54:38AM -0700, Linus Torvalds wrote:
> On Wed, May 3, 2023 at 9:38 AM Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > So I'm going to just remove the 'sign' games entirely. They are
> > completely broken in 'untagged_addr_remote()', they _used_ to be
> > completely broken in 'untagged_addr()', and it looks like it's all
> > unnecessary.
> 
> Ok, I've pushed out my changes to the 'x86-uaccess-cleanup' branch.
> 
> I think it's all good, but it would be really nice to hear it's been
> tested on a setup that actually has LAM (simulator? or maybe there is
> actual hw inside Intel)
> 
> And any other commentary is appreciated,

Looks sane from a first reading. But I'll try and have another look
tomorrow.

Also per how 2s complement is constructed 0 has to be in the positive
space for it to be 'half'. Also, typically 0 is included in N and the
traditional 'positive integers' set is then written as N \ {0}, but
that's somewhat modern and a lot of variation exists -- although
typically books tend to specify where they stand on that issue.

I suppose that's a very long winded way of saying, that yes, ofcourse 0
is a positive number :-)