From: Ulrich Weigand <weigand@immd1.informatik.uni-erlangen.de>
To: zaitcev@redhat.com
Cc: schwidefsky@de.ibm.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] s390 (5/7): kmalloc arguments.
Date: Fri, 7 Mar 2003 22:13:23 +0100 (MET) [thread overview]
Message-ID: <200303072113.WAA08451@faui11.informatik.uni-erlangen.de> (raw)
Pete Zaitcev wrote:
>What does GFP_DMA do on s390 and s390x?
On s390, nothing.
On s390x, it makes sure the allocated memory resides at
addresses below 2 GB. This is necessary, as many of the
I/O subsystem data structures as defined by the hardware
contain pointer fields that are still 31-bit, even on
64-bit machines. Thus we have to make sure those data
structures are allocated below 2 GB. Using the GFP_DMA
mechanism for that purpose seemed to be the way to go ...
Note that contrary to the usual purpose of GFP_DMA on Intel,
the actual *data* that is being transferred via the I/O
subsystem can reside at arbitrary addresses (which are
specified via indirect-addressing lists); it is only the
control data structures that need to go below 2 GB.
Bye,
Ulrich
--
Dr. Ulrich Weigand
weigand@informatik.uni-erlangen.de
next reply other threads:[~2003-03-07 21:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-03-07 21:13 Ulrich Weigand [this message]
[not found] <mailman.1047042481.25045.linux-kernel2news@redhat.com>
2003-03-07 20:08 ` [PATCH] s390 (5/7): kmalloc arguments Pete Zaitcev
-- strict thread matches above, loose matches on Subject: below --
2003-03-07 12:38 Martin Schwidefsky
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