archive mirror
 help / color / mirror / Atom feed
From: "Krzysztof Hałasa" <>
To: "Russell King (Oracle)" <>
Cc: linux-arm-kernel <>,
	lkml <>
Subject: Re: Data corruption on i.MX6 IPU in arm_copy_from_user()
Date: Mon, 31 May 2021 06:30:10 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <> (Russell King's message of "Fri, 28 May 2021 15:35:44 +0100")

"Russell King (Oracle)" <> writes:

>> LDM12: 1 3 4 5 6 7 8 9 A B C D
> That's rather sad, and does look very much like a hardware bug.
> The question is what to do about it... there's Linus' "do not break
> userspace" edict and that's exactly what this change has done. So I
> suppose we're going to have to revert the change and put up with
> everything being slightly slower on arm32 than it otherwise would
> have been. That probably means we'll end up with almost every kernel
> tree out there carrying a revert of the revert to work around the
> fact that seemingly NXP broke their hardware - which itself is not
> a good idea. I guess we're just going to have to put up with that.

For userspace, it's quite a corner case, basically development-only -
and I guess there are very few people who will do things like this.

The same problem can manifest itself without any kernel involvement -
it's enough to mmap /dev/mem and use LDM on in completely in userspace.
This can't be fixed - unless we disallow IPU mmap.

Perhaps making sure the bug is clearly documented is better than doing
a partial fix. Ideally NXP should document it in their papers, and we
should add notes to IPU driver code.

The last one - I guess I can do.
Krzysztof Hałasa

Sieć Badawcza Łukasiewicz
Przemysłowy Instytut Automatyki i Pomiarów PIAP
Al. Jerozolimskie 202, 02-486 Warszawa

  reply	other threads:[~2021-05-31  4:30 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-26  8:26 Krzysztof Hałasa
2021-05-26 10:08 ` Russell King (Oracle)
2021-05-26 12:29   ` Krzysztof Hałasa
2021-05-26 13:18     ` Russell King (Oracle)
2021-05-27 14:06       ` David Laight
2021-05-28 10:02       ` Krzysztof Hałasa
2021-05-28 14:35         ` Russell King (Oracle)
2021-05-31  4:30           ` Krzysztof Hałasa [this message]
2021-05-31  6:20           ` Krzysztof Hałasa

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:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \
    --subject='Re: Data corruption on i.MX6 IPU in arm_copy_from_user()' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

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).