Subject: Re: port-arm/36513: Pre-cache load length exceeds source memory area in memcpy
To: None <scw@NetBSD.org, gnats-admin@netbsd.org, netbsd-bugs@netbsd.org,>
From: Masao Uebayashi <uebayasi@gmail.com>
List: netbsd-bugs
Date: 06/20/2007 08:50:03
The following reply was made to PR port-arm/36513; it has been noted by GNATS.

From: "Masao Uebayashi" <uebayasi@gmail.com>
To: "Steve Woodford" <scw@netbsd.org>
Cc: gnats-bugs@netbsd.org, port-arm-maintainer@netbsd.org,
	gnats-admin@netbsd.org, netbsd-bugs@netbsd.org
Subject: Re: port-arm/36513: Pre-cache load length exceeds source memory area in memcpy
Date: Wed, 20 Jun 2007 17:49:06 +0900

 I'm not Doshita-san, but it was me who translated with confusion, so...
 
 > > Pre-cache load length exceeds source memory area in memcpy.
 > > Unrelated area is written back to memory, which causes
 > > some troubles.
 >
 > Can you elaborate on the "some troubles" part? The source cacheline will
 > not be marked dirty by pld, assuming it was already clean or not
 > resident in the cache to begin with, so a write-back will not occur.
 
 "Write-back" was wrong.  This is all about read (cache fill).
 
 > The only case I can think of where this *may* be an issue would be
 > copying from a cacheable memory region which is shared with a
 > DMA-capable device...
 
 The place he had problem was a memcpy() in m_dup(9).  The memcpy() does
 its job correctly, but something slow happens there and the system loses
 lots of packets.  We guess it's kind of exception, but have not figured out yet.
 
 Masao