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Re: 64 bit operations w/32 bit kernel

To: Ralf Baechle <>
Subject: Re: 64 bit operations w/32 bit kernel
From: "Maciej W. Rozycki" <>
Date: Tue, 30 Sep 2003 20:04:42 +0200 (MET DST)
Cc: "Finney, Steve" <Steve.Finney@SpirentCom.COM>,
In-reply-to: <>
Organization: Technical University of Gdansk
Original-recipient: rfc822;
On Tue, 30 Sep 2003, Ralf Baechle wrote:

> > What would be the downside to enabling 64 bit operations in user space
> > on a 32 bit kernel (setting the PX bit in the status register?). The
> > particular issue is that I want to access 64 bit-memory mapped registers,
> > and I really need to do it as an atomic operation. I tried borrowing
> > sibyte/64bit.h from the kernel, but I get an illegal instruction on the
> > double ops.
> Common design bug in hardware, imho ...

 Well, ioremap() can be used to get at these areas (as well as any
others), whether we call it a bug or not.

+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+        e-mail:, PGP key available        +

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