From: "Gerhard Pircher" <gerhard_pircher@gmx•net>
To: Andrew Lewis <andrew-lewis@netspace•net.au>, linuxppc-dev@ozlabs•org
Cc: paulus@samba•org
Subject: Re: [PATCH/RFC] powerpc: prevent memory corruption due to cache invalidation of unaligned DMA buffer
Date: Thu, 26 Jun 2008 12:32:15 +0200 [thread overview]
Message-ID: <20080626103215.170810@gmx.net> (raw)
In-Reply-To: <48636161.6080603@netspace.net.au>
-------- Original-Nachricht --------
> Datum: Thu, 26 Jun 2008 17:29:05 +0800
> Von: Andrew Lewis <andrew-lewis@netspace•net.au>
> An: linuxppc-dev@ozlabs•org
> CC: \'Andrew Lewis\' <andrew-lewis@netspace•net.au>, paulus@samba•org
> Betreff: [PATCH/RFC] powerpc: prevent memory corruption due to cache invalidation of unaligned DMA buffer
> On PowerPC processors with non-coherent cache architectures the DMA
> subsystem calls invalidate_dcache_range() before performing a DMA read
> operation. If the address and length of the DMA buffer are not aligned
> to a cache-line boundary this can result in memory outside of the DMA
> buffer being invalidated in the cache. If this memory has an
> uncommitted store then the data will be lost and a subsequent read of
> that address will result in an old value being returned from main memory.
>
> Only when the DMA buffer starts on a cache-line boundary and is an exact
> mutiple of the cache-line size can invalidate_dcache_range() be called,
> otherwise flush_dcache_range() must be called. flush_dcache_range()
> will first flush uncommitted writes, and then invalidate the cache.
I have a similar problem, but with a network driver (which uses cacheable
skbuffers as DMA memory). The SLUB allocator should return cache line
aligned memory, but that doesn't prevent data corruption. I fixed it by
setting NET_SKB_PAD (default 16) to L1_CACHE_BYTES (32 on my 7455
non coherent DMA system).
It looks like your patch could solve my problem without changing
NET_SKB_PAD. I'll have to try that out.
regards,
Gerhard
--
Ist Ihr Browser Vista-kompatibel? Jetzt die neuesten
Browser-Versionen downloaden: http://www.gmx.net/de/go/browser
next prev parent reply other threads:[~2008-06-26 11:20 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-26 9:29 [PATCH/RFC] powerpc: prevent memory corruption due to cache invalidation of unaligned DMA buffer Andrew Lewis
2008-06-26 10:32 ` Gerhard Pircher [this message]
2008-06-26 10:55 ` Benjamin Herrenschmidt
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=20080626103215.170810@gmx.net \
--to=gerhard_pircher@gmx$(echo .)net \
--cc=andrew-lewis@netspace$(echo .)net.au \
--cc=linuxppc-dev@ozlabs$(echo .)org \
--cc=paulus@samba$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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