From: Mikulas Patocka <mpatocka@redhat.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
Joao Pinto <Joao.Pinto@synopsys.com>,
libc-alpha@sourceware.org,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Jingoo Han <jingoohan1@gmail.com>,
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@vger.kernel.org,
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 14:40:16 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.1808081437260.18198@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <20180808142852.GD24736@iMac.local>
On Wed, 8 Aug 2018, Catalin Marinas wrote:
> On Wed, Aug 08, 2018 at 10:12:27AM -0400, Mikulas Patocka wrote:
> > On Wed, 8 Aug 2018, Catalin Marinas wrote:
> > > On Fri, Aug 03, 2018 at 01:09:02PM -0400, Mikulas Patocka wrote:
> > > > while (1) {
> > > > start = (unsigned)random() % (LEN + 1);
> > > > end = (unsigned)random() % (LEN + 1);
> > > > if (start > end)
> > > > continue;
> > > > for (i = start; i < end; i++)
> > > > data[i] = val++;
> > > > memcpy(map + start, data + start, end - start);
> > > > if (memcmp(map, data, LEN)) {
> > >
> > > It may be worth trying to do a memcmp(map+start, data+start, end-start)
> > > here to see whether the hazard logic fails when the writes are unaligned
> > > but the reads are not.
> > >
> > > This problem may as well appear if you do byte writes and read longs
> > > back (and I consider this a hardware problem on this specific board).
> >
> > I triad to insert usleep(10000) between the memcpy and memcmp, but the
> > same corruption occurs. So, it can't be read-after-write hazard. It is
> > caused by the improper handling of hazard between the overlapping writes
> > inside memcpy.
>
> It could get it wrong between subsequent writes to the same 64-bit range
> (e.g. the address & ~63 is the same but the data strobes for which bytes
> to write are different). If it somehow thinks that it's a
> write-after-write hazard even though the strobes are different, it could
> cancel one of the writes.
I believe that the SoC has logic for write-after-write detection, but the
logic is broken and corrupts data.
If I insert "dmb sy" between the overlapping writes, there's no corruption
(the PCIe controller won't see any overlapping writes in that case).
> It may be worth trying with a byte-only memcpy() function while keeping
> the default memcmp().
I tried that and byte-only memcpy works without any corruption.
> --
> Catalin
Mikulas
next prev parent reply other threads:[~2018-08-08 18:40 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
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 [this message]
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
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