linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Mikulas Patocka <mpatocka@redhat.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Laight <David.Laight@ACULAB.COM>,
	Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
	Joao Pinto <Joao.Pinto@synopsys.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Will Deacon <will.deacon@arm.com>,
	Russell King <linux@armlinux.org.uk>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Matt Sealey <neko@bakuhatsu.net>,
	linux-pci <linux-pci@vger.kernel.org>,
	Jingoo Han <jingoohan1@gmail.com>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: framebuffer corruption due to overlapping stp instructions on arm64
Date: Wed, 8 Aug 2018 12:21:31 -0400 (EDT)	[thread overview]
Message-ID: <alpine.LRH.2.02.1808081215120.31259@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <20180808145017.GE24736@iMac.local>



On Wed, 8 Aug 2018, Catalin Marinas wrote:

> On Wed, Aug 08, 2018 at 02:26:11PM +0000, David Laight wrote:
> > From: Mikulas Patocka
> > > Sent: 08 August 2018 14:47
> > ...
> > > The problem on ARM is that I see data corruption when the overlapping
> > > unaligned writes are done just by a single core.
> > 
> > Is this a sequence of unaligned writes (that shouldn't modify the
> > same physical locations) or an aligned write followed by an
> > unaligned one that updates part of the earlier write.
> > (Or the opposite order?)
> 
> In the memcpy() case, there can be a sequence of unaligned writes but
> they would not modify the same byte (so no overlapping address at the
> byte level).

They do modify the same byte, but with the same value. Suppose that you 
want to copy a piece of data that is between 8 and 16 bytes long. You can 
do this:

add src_end, src, len
add dst_end, dst, len
ldr x0, [src]
ldr x1, [src_end - 8]
str x0, [dst]
str x1, [dst_end - 8]

The ARM64 memcpy uses this trick heavily in order to reduce branching, and 
this is what makes the PCIe controller choke.

Mikulas

  reply	other threads:[~2018-08-08 16:21 UTC|newest]

Thread overview: 95+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-02 19:31 framebuffer corruption due to overlapping stp instructions on arm64 Mikulas Patocka
     [not found] ` <CAHCPf3tFGqkYEcWNN4LaWThw_rVqT316pzLv6T7RfxwO-eZ0EA@mail.gmail.com>
2018-08-03  6:35   ` Mikulas Patocka
2018-08-03  7:16     ` Ard Biesheuvel
2018-08-03  9:41       ` Will Deacon
2018-08-03 17:09         ` Mikulas Patocka
2018-08-03 17:32           ` Sinan Kaya
2018-08-03 17:33           ` Ard Biesheuvel
2018-08-03 18:25             ` Mikulas Patocka
2018-08-03 20:44               ` Matt Sealey
2018-08-03 21:20                 ` Ard Biesheuvel
2018-08-06 10:25                   ` Mikulas Patocka
2018-08-06 12:42                     ` Robin Murphy
2018-08-06 12:53                       ` Ard Biesheuvel
2018-08-06 13:41                       ` Marcin Wojtas
2018-08-06 13:48                         ` Ard Biesheuvel
2018-08-06 14:07                           ` Marcin Wojtas
2018-08-06 14:13                             ` Mikulas Patocka
2018-08-06 15:47                       ` Ard Biesheuvel
2018-08-06 17:09                         ` Mikulas Patocka
2018-08-06 17:21                           ` Ard Biesheuvel
2018-08-06 19:54                             ` Mikulas Patocka
2018-08-06 20:11                               ` Ard Biesheuvel
2018-08-06 20:31                                 ` Mikulas Patocka
2018-08-07 16:40                                 ` Marcin Wojtas
2018-08-07 17:39                                   ` Mikulas Patocka
2018-08-07 18:07                                     ` Ard Biesheuvel
2018-08-07 18:17                                       ` Mikulas Patocka
     [not found]                                     ` <CAPv3WKcKoEe=Qysp6Oac2C=G9bUhUQf1twSRCY+_qJ6XEC-iag@mail.gmail.com>
2018-08-08 14:10                                       ` Mikulas Patocka
2018-08-06 17:13                         ` Catalin Marinas
2018-08-06 17:19                           ` Mikulas Patocka
2018-08-08 18:31                       ` Mikulas Patocka
2018-08-04 13:29                 ` Mikulas Patocka
2018-08-08 12:16                 ` Catalin Marinas
2018-08-08 13:02                   ` David Laight
2018-08-08 13:46                     ` Mikulas Patocka
2018-08-08 14:26                       ` David Laight
2018-08-08 14:50                         ` Catalin Marinas
2018-08-08 16:21                           ` Mikulas Patocka [this message]
2018-08-08 16:31                             ` Arnd Bergmann
2018-08-08 16:43                               ` David Laight
2018-08-08 18:56                                 ` Mikulas Patocka
2018-08-08 18:37                         ` Mikulas Patocka
2018-08-08 11:39           ` Catalin Marinas
2018-08-08 14:12             ` Mikulas Patocka
2018-08-08 14:28               ` Catalin Marinas
2018-08-08 18:40                 ` Mikulas Patocka
2018-08-08 15:01               ` Richard Earnshaw (lists)
2018-08-08 15:14                 ` Catalin Marinas
2018-08-08 16:01                   ` Arnd Bergmann
2018-08-08 18:25                     ` Mikulas Patocka
2018-08-08 21:51                       ` Arnd Bergmann
2018-08-09 15:29                         ` Arnd Bergmann
2018-08-03  7:11 ` Andrew Pinski
2018-08-03  7:53   ` Florian Weimer
2018-08-03  9:12     ` Szabolcs Nagy
2018-08-03  9:15     ` Ramana Radhakrishnan
2018-08-03  9:29       ` Ard Biesheuvel
2018-08-03  9:37         ` Ramana Radhakrishnan
2018-08-03  9:42         ` Richard Earnshaw (lists)
2018-08-04  0:58           ` Mikulas Patocka
2018-08-04  1:13             ` Andrew Pinski
2018-08-04 11:04               ` Mikulas Patocka
2018-08-05 18:33                 ` Florian Weimer
2018-08-06  8:02                   ` Mikulas Patocka
2018-08-06  8:10                     ` Ard Biesheuvel
2018-08-06 10:31                       ` Mikulas Patocka
2018-08-06 10:37                         ` Ard Biesheuvel
2018-08-06 10:42                           ` Mikulas Patocka
2018-08-06 10:48                             ` Ard Biesheuvel
2018-08-06 12:09                               ` Mikulas Patocka
2018-08-06 12:19                                 ` Ard Biesheuvel
2018-08-06 12:22                                   ` Ard Biesheuvel
2018-08-07 14:14                                   ` Mikulas Patocka
2018-08-07 14:40                                     ` Ard Biesheuvel
2018-08-08 19:15                                   ` Mikulas Patocka
2018-08-06 11:19                         ` Siddhesh Poyarekar
2018-08-06 11:29                           ` Ard Biesheuvel
2018-08-06 14:26                   ` Tulio Magno Quites Machado Filho
2018-08-05 21:51                 ` Pavel Machek
2018-08-06 14:30                   ` Mikulas Patocka
2018-08-03 11:24         ` David Laight
2018-08-03 12:04           ` Mikulas Patocka
2018-08-03 13:04             ` David Laight
2018-08-05 14:36               ` Mikulas Patocka
2018-08-06 10:18                 ` David Laight
2018-08-07 14:07                   ` Mikulas Patocka
2018-08-07 14:33                     ` David Laight
2018-08-08 14:21                       ` Mikulas Patocka
2018-08-03 13:20     ` Mikulas Patocka
2018-08-03 13:31   ` Mikulas Patocka
2018-08-03 14:17     ` Richard Earnshaw (lists)
2018-08-05 21:36   ` Pavel Machek
2018-08-06  8:04     ` Ramana Radhakrishnan
2018-08-06  8:44       ` Pavel Machek
2018-08-06  9:11         ` 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=alpine.LRH.2.02.1808081215120.31259@file01.intranet.prod.int.rdu2.redhat.com \
    --to=mpatocka@redhat.com \
    --cc=David.Laight@ACULAB.COM \
    --cc=Joao.Pinto@synopsys.com \
    --cc=ard.biesheuvel@linaro.org \
    --cc=catalin.marinas@arm.com \
    --cc=jingoohan1@gmail.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=linux@armlinux.org.uk \
    --cc=neko@bakuhatsu.net \
    --cc=thomas.petazzoni@free-electrons.com \
    --cc=will.deacon@arm.com \
    /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).