From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: kernelci-results@groups.io,
Geert Uytterhoeven <geert+renesas@glider.be>,
Nicolas Pitre <nico@fluxnic.net>, Marc Zyngier <maz@kernel.org>,
Linus Walleij <linus.walleij@linaro.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Guillaume Tucker <guillaume.tucker@collabora.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: next/master bisection: baseline.login on rk3288-rock2-square
Date: Thu, 4 Feb 2021 14:36:18 +0000 [thread overview]
Message-ID: <20210204143618.GY1463@shell.armlinux.org.uk> (raw)
In-Reply-To: <CAMj1kXHf0dNvsrfct6rCxi_yHXcQCqjwJoMa_TD0Fh6xo2zeZQ@mail.gmail.com>
On Thu, Feb 04, 2021 at 03:25:20PM +0100, Ard Biesheuvel wrote:
> Pushing contents of the cache hierarchy to main memory is *not* a
> valid use of set/way ops, and so there is no point in pretending that
> set/way ops will produce the same results as by-VA ops. Only the by-VA
> ops give the architectural guarantees that we rely on for correctness.
... yet we /were/ doing that, and it worked fine for 13 years - from
1st June 2007 until the by-VA merge into mainline on the 3rd April
2020.
You may be right that it wasn't the most correct way, but it worked
for those 13 years without issue, and it's only recently that it's
become a problem, and trying to "fix" that introduced a regression,
and fixing that regression has caused another regression... and I
what I'm wondering is how many more regression fixing cycles it's
going to take - how many regression fixes on top of other regression
fixes are we going to end up seeing here.
The fact is, we never properly understood why your patch caused the
regression I was seeing. If we don't understand it, then we can never
say that we've fixed the problem properly. That is highlighted by the
fact that fixing the regression I was seeing has caused another
regression.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-02-04 14:40 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <601b773a.1c69fb81.9f381.a32a@mx.google.com>
2021-02-04 8:43 ` next/master bisection: baseline.login on rk3288-rock2-square Guillaume Tucker
2021-02-04 9:07 ` Ard Biesheuvel
2021-02-04 10:06 ` Russell King - ARM Linux admin
2021-02-04 10:27 ` Ard Biesheuvel
2021-02-04 10:33 ` Guillaume Tucker
2021-02-04 11:32 ` Guillaume Tucker
2021-02-04 11:44 ` Russell King - ARM Linux admin
2021-02-04 12:09 ` Ard Biesheuvel
2021-02-04 15:42 ` Ard Biesheuvel
2021-02-04 15:53 ` Guillaume Tucker
2021-02-04 16:01 ` Ard Biesheuvel
2021-02-04 18:06 ` Nick Desaulniers
2021-02-04 18:12 ` Nathan Chancellor
2021-02-04 18:23 ` Nick Desaulniers
2021-02-04 21:31 ` Guillaume Tucker
2021-02-04 21:50 ` Russell King - ARM Linux admin
2021-02-05 8:21 ` Ard Biesheuvel
2021-02-05 12:05 ` Ard Biesheuvel
2021-02-06 13:10 ` Guillaume Tucker
2021-02-06 13:12 ` Ard Biesheuvel
2021-02-04 21:09 ` Guillaume Tucker
2021-02-04 10:47 ` Russell King - ARM Linux admin
2021-02-04 10:55 ` Ard Biesheuvel
2021-02-04 12:26 ` Marc Zyngier
2021-02-04 14:09 ` Russell King - ARM Linux admin
2021-02-04 14:25 ` Ard Biesheuvel
2021-02-04 14:36 ` Russell King - ARM Linux admin [this message]
2021-02-04 15:52 ` Ard Biesheuvel
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=20210204143618.GY1463@shell.armlinux.org.uk \
--to=linux@armlinux.org.uk \
--cc=ardb@kernel.org \
--cc=geert+renesas@glider.be \
--cc=guillaume.tucker@collabora.com \
--cc=kernelci-results@groups.io \
--cc=linus.walleij@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=maz@kernel.org \
--cc=nico@fluxnic.net \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).