From: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
To: "Maciej W. Rozycki" <macro@orcam.me.uk>
Cc: Nick Bowler <nbowler@draconx.ca>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] MIPS: mm: Prevent a TLB shutdown on initial uniquification
Date: Tue, 11 Nov 2025 23:53:00 +0100 [thread overview]
Message-ID: <aRO-TDaljXzgZfps@alpha.franken.de> (raw)
In-Reply-To: <alpine.DEB.2.21.2511111340330.25436@angie.orcam.me.uk>
On Tue, Nov 11, 2025 at 03:41:50PM +0000, Maciej W. Rozycki wrote:
> On Tue, 11 Nov 2025, Thomas Bogendoerfer wrote:
>
> > > Can you please give it a try with your systems?
> >
> > it's booting on my R4400 SGI Indy, but I see a lot of segmentation
> > faults during system start. If I comment out r4k_tlb_uniquify() every-
> > thing boots fine, which is kind of strange as there is a local_flush_tlb_all(),
> > which should leave the TLB in the same stage.... No idea why, yet.
>
> Can you try the diagnostic patch below, which is what I used to verify
> this change, and report the entries produced? Otherwise I wonder whether
> I haven't missed a barrier somewhere.
output below, I don't see anything obvious. I dumped the TLB after the
local_flush_tlb_all() and everything looks as before.
>
> > > +
> > > + for (i = start, cnt = 0; i < tlbsize; i++, cnt++) {
> >
> > shouldn't we read all TLB entries here ?
>
> Strictly speaking it won't change anything as we call `write_c0_wired(0)'
> in `r4k_tlb_configure' before getting here and wired entries make no sense
> for KSEG0, so whatever would otherwise be there should not clash with our
> unique entries.
I see
> NB I wonder how this is supposed to work with mapped kernels, I thought
> the setup made with MAPPED_KERNEL_SETUP_TLB was meant to be permanent
> through the life of the system, hmm...
I looked at it once some time ago and already forgot details :-(
Thomas.
[00/00]: 80000000/80000000
[01/01]: 80000000/80000000
[02/02]: 80000000/80000000
[03/03]: 80000000/80000000
[04/04]: 80000000/80000000
[05/05]: 80000000/80000000
[06/06]: 80000000/80000000
[07/07]: 80000000/80000000
[08/08]: 80000000/80000000
[09/09]: 80000000/80000000
[0a/0a]: 80000000/80000000
[0b/0b]: 80000000/80000000
[0c/0c]: 80000000/80000000
[0d/0d]: 80000000/80000000
[0e/0e]: 80000000/80000000
[0f/0f]: 80000000/80000000
[10/10]: 80000000/80000000
[11/11]: 80000000/80000000
[12/12]: 80000000/80000000
[13/13]: 80000000/80000000
[14/14]: 80000000/80000000
[15/15]: 80000000/80000000
[16/16]: 80000000/80000000
[17/17]: 80000000/80000000
[18/18]: 80000000/80000000
[19/19]: 80000000/80000000
[1a/1a]: 80000000/80000000
[1b/1b]: 80000000/80000000
[1c/1c]: 80000000/80000000
[1d/1d]: 80000000/80000000
[1e/1e]: 80000000/80000000
[1f/1f]: 80000000/80000000
[20/20]: 80000000/80000000
[21/21]: 80000000/80000000
[22/22]: 80000000/80000000
[23/23]: 80000000/80000000
[24/24]: 80000000/80000000
[25/25]: 80000000/80000000
[26/26]: 80000000/80000000
[27/27]: 80000000/80000000
[28/28]: 80000000/80000000
[29/29]: 80000000/80000000
[2a/2a]: 80000000/80000000
[2b/2b]: 80000000/80000000
[2c/2c]: 80000000/80000000
[2d/2d]: 80000000/80000000
[2e/2e]: 80000000/80000000
[2f/2f]: 80000000/80000000
[00]: 80000000
[01]: 80000000
[02]: 80000000
[03]: 80000000
[04]: 80000000
[05]: 80000000
[06]: 80000000
[07]: 80000000
[08]: 80000000
[09]: 80000000
[0a]: 80000000
[0b]: 80000000
[0c]: 80000000
[0d]: 80000000
[0e]: 80000000
[0f]: 80000000
[10]: 80000000
[11]: 80000000
[12]: 80000000
[13]: 80000000
[14]: 80000000
[15]: 80000000
[16]: 80000000
[17]: 80000000
[18]: 80000000
[19]: 80000000
[1a]: 80000000
[1b]: 80000000
[1c]: 80000000
[1d]: 80000000
[1e]: 80000000
[1f]: 80000000
[20]: 80000000
[21]: 80000000
[22]: 80000000
[23]: 80000000
[24]: 80000000
[25]: 80000000
[26]: 80000000
[27]: 80000000
[28]: 80000000
[29]: 80000000
[2a]: 80000000
[2b]: 80000000
[2c]: 80000000
[2d]: 80000000
[2e]: 80000000
[2f]: 80000000
[00/00/30]: 80060000/80000000
[00/01/30]: 80060000/80000000
[00/02/30]: 80060000/80000000
[00/03/30]: 80060000/80000000
[00/04/30]: 80060000/80000000
[00/05/30]: 80060000/80000000
[00/06/30]: 80060000/80000000
[00/07/30]: 80060000/80000000
[00/08/30]: 80060000/80000000
[00/09/30]: 80060000/80000000
[00/0a/30]: 80060000/80000000
[00/0b/30]: 80060000/80000000
[00/0c/30]: 80060000/80000000
[00/0d/30]: 80060000/80000000
[00/0e/30]: 80060000/80000000
[00/0f/30]: 80060000/80000000
[00/10/30]: 80060000/80000000
[00/11/30]: 80060000/80000000
[00/12/30]: 80060000/80000000
[00/13/30]: 80060000/80000000
[00/14/30]: 80060000/80000000
[00/15/30]: 80060000/80000000
[00/16/30]: 80060000/80000000
[00/17/30]: 80060000/80000000
[00/18/30]: 80060000/80000000
[00/19/30]: 80060000/80000000
[00/1a/30]: 80060000/80000000
[00/1b/30]: 80060000/80000000
[00/1c/30]: 80060000/80000000
[00/1d/30]: 80060000/80000000
[00/1e/30]: 80060000/80000000
[00/1f/30]: 80060000/80000000
[00/20/30]: 80060000/80000000
[00/21/30]: 80060000/80000000
[00/22/30]: 80060000/80000000
[00/23/30]: 80060000/80000000
[00/24/30]: 80060000/80000000
[00/25/30]: 80060000/80000000
[00/26/30]: 80060000/80000000
[00/27/30]: 80060000/80000000
[00/28/30]: 80060000/80000000
[00/29/30]: 80060000/80000000
[00/2a/30]: 80060000/80000000
[00/2b/30]: 80060000/80000000
[00/2c/30]: 80060000/80000000
[00/2d/30]: 80060000/80000000
[00/2e/30]: 80060000/80000000
[00/2f/30]: 80060000/80000000
[00/30/30]: 80060000/00010000
[01/30/31]: 80062000/00010000
[02/30/32]: 80064000/00010000
[03/30/33]: 80066000/00010000
[04/30/34]: 80068000/00010000
[05/30/35]: 8006a000/00010000
[06/30/36]: 8006c000/00010000
[07/30/37]: 8006e000/00010000
[08/30/38]: 80070000/00010000
[09/30/39]: 80072000/00010000
[0a/30/3a]: 80074000/00010000
[0b/30/3b]: 80076000/00010000
[0c/30/3c]: 80078000/00010000
[0d/30/3d]: 8007a000/00010000
[0e/30/3e]: 8007c000/00010000
[0f/30/3f]: 8007e000/00010000
[10/30/40]: 80080000/00010000
[11/30/41]: 80082000/00010000
[12/30/42]: 80084000/00010000
[13/30/43]: 80086000/00010000
[14/30/44]: 80088000/00010000
[15/30/45]: 8008a000/00010000
[16/30/46]: 8008c000/00010000
[17/30/47]: 8008e000/00010000
[18/30/48]: 80090000/00010000
[19/30/49]: 80092000/00010000
[1a/30/4a]: 80094000/00010000
[1b/30/4b]: 80096000/00010000
[1c/30/4c]: 80098000/00010000
[1d/30/4d]: 8009a000/00010000
[1e/30/4e]: 8009c000/00010000
[1f/30/4f]: 8009e000/00010000
[20/30/50]: 800a0000/00010000
[21/30/51]: 800a2000/00010000
[22/30/52]: 800a4000/00010000
[23/30/53]: 800a6000/00010000
[24/30/54]: 800a8000/00010000
[25/30/55]: 800aa000/00010000
[26/30/56]: 800ac000/00010000
[27/30/57]: 800ae000/00010000
[28/30/58]: 800b0000/00010000
[29/30/59]: 800b2000/00010000
[2a/30/5a]: 800b4000/00010000
[2b/30/5b]: 800b6000/00010000
[2c/30/5c]: 800b8000/00010000
[2d/30/5d]: 800ba000/00010000
[2e/30/5e]: 800bc000/00010000
[2f/30/5f]: 800be000/00010000
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
next prev parent reply other threads:[~2025-11-11 22:53 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-11 6:21 [PATCH] MIPS: mm: Prevent a TLB shutdown on initial uniquification Maciej W. Rozycki
2025-11-11 12:27 ` Thomas Bogendoerfer
2025-11-11 15:41 ` Maciej W. Rozycki
2025-11-11 22:53 ` Thomas Bogendoerfer [this message]
2025-11-12 9:56 ` Thomas Bogendoerfer
2025-11-12 12:16 ` Maciej W. Rozycki
2025-11-12 14:20 ` Thomas Bogendoerfer
2025-11-12 23:47 ` Maciej W. Rozycki
2025-11-11 22:17 ` Nick Bowler
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=aRO-TDaljXzgZfps@alpha.franken.de \
--to=tsbogend@alpha.franken.de \
--cc=jiaxun.yang@flygoat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mips@vger.kernel.org \
--cc=macro@orcam.me.uk \
--cc=nbowler@draconx.ca \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.