From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Wed, 09 Apr 2003 17:33:59 +0000 Subject: Re: [Linux-ia64] mmap crashes system after mapping PCI device into user space and reading and writin Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Tue, 8 Apr 2003 17:59:56 -0400, "Mike Fox" said: Mike> Hi, I am running kernel version 2.4.19 and I am getting a Mike> system crash when I mmap my PCI device into user space and Mike> access it. One thing you need to be careful about is memory attribute aliasing. The CPU (or platform chips) can MCA if you try to access the same physical location with different memory attributes (e.g., cached vs. uncached). Also, keep in mind that the kernel uses a 64MB page size for the identity-mapped regions (regions 6 and 7). This means that you cannot map stuff requiring different attributes within the same 64MB page. I kind of doubt this is what's causing the problem for you, but since you didn't give any details about the hw you're trying to map, it's hard to be more specific. As others have pointed out, it's of course also important to verify that you access I/O space uncached. --david