linux-kernel - Re: [PATCH v2 3/5] mips: Print the kernel virtual mem layout on debugging

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Message-ID: <20190617133929.uz7fweirm4a6oqnk@mobilestation>
Date:   Mon, 17 Jun 2019 16:39:30 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Paul Burton <paul.burton@...s.com>
Cc:     Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Bogendoerfer <tbogendoerfer@...e.de>,
        Huacai Chen <chenhc@...ote.com>,
        Stefan Agner <stefan@...er.ch>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Juergen Gross <jgross@...e.com>,
        Serge Semin <Sergey.Semin@...latforms.ru>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] mips: Print the kernel virtual mem layout on
 debugging

Hello Paul

On Wed, May 08, 2019 at 02:38:49AM +0300, Serge Semin wrote:
> On Tue, May 07, 2019 at 10:41:10PM +0000, Paul Burton wrote:
> > Hi Serge,
> > 
> > On Wed, May 08, 2019 at 01:36:07AM +0300, Serge Semin wrote:
> > > Thanks for the report regarding this issue. I actually thought I
> > > tested the patch being buildable for 64bit systems. It turns out I
> > > didn't.(
> > 
> > Easily done :)
> > 
> > > Should I resend the fixed patch as a separate v3 one In-Reply-to this
> > > v2 patch or resubmit the patchset with cover-letter and only the fixed
> > > patch being there?
> > 
> > Replying with just v3 of this patch will be fine, no need to resend the
> > cover letter.
> > 
> 
> Ok. I've just submitted the v3 version with fixed buildability problem.
> 
> > I currently plan to submit a pull request for mips-next as-is, without
> > this patch, in the next day or two. There are a few last minute
> > submissions this time round that I'll then queue up & send a second pull
> > request next week, which this can be part of.
> > 
> > Thanks,
> >     Paul
> 
> Regarding this patch being part of the mips mm init code. I've just found out
> that 32-bit arm subsystem maintainers removed the same functionality from the
> kernel 5.1. This also was removed from arm64 in kernel 4.15:
> commit 1c31d4e96b8c ("ARM: 8820/1: mm: Stop printing the virtual memory layout")
> commit 071929dbdd86 ("arm64: Stop printing the virtual memory layout")
> 
> Maintainer of m68k and unicore32 discarded the printing as well:
> commit 1476ea250cf0 ("unicore32: stop printing the virtual memory layout")
> commit 31833332f798 ("m68k/mm: Stop printing the virtual memory layout")
> 
> The reasoning of these removal was that since commit ad67b74d2469 ("printk:
> hash addresses printed with %p") the kernel virtual addresses weren't
> printed to the system log anyway. So instead of replacing the format string with
> "%px" they decided not to leak a virtual memory layout information and completely
> removed the printing. I don't really know why they didn't closed the printing for
> debug kernel only as we did, since the info might be useful in this case.
> 
> Since I see a tendency of this functionality removal, we might need to
> reconsider this patch integration into the MIPS arch code. What do you think?
> 
> Although some architectures still perform the virtual memory layout printing
> at boot-time: x86_32, parisc, xtensa, sh, nds32 (might be others).
> 
> Cheers,
> -Sergey

So any update on this patch status?

Regards,
-Sergey