linux-kernel - Re: framebuffer corruption due to overlapping stp instructions on arm64

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Date:   Wed, 8 Aug 2018 15:50:17 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     'Mikulas Patocka' <mpatocka@...hat.com>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Russell King <linux@...linux.org.uk>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Matt Sealey <neko@...uhatsu.net>,
        linux-pci <linux-pci@...r.kernel.org>,
        Jingoo Han <jingoohan1@...il.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: framebuffer corruption due to overlapping stp instructions on
 arm64

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).

-- 
Catalin