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Re: [BUG?] cavium cn56xx and dma_map_single warning

To: Zhuang Yuyao <>
Subject: Re: [BUG?] cavium cn56xx and dma_map_single warning
From: David Daney <>
Date: Mon, 22 Mar 2010 18:39:19 -0700
In-reply-to: <>
Original-recipient: rfc822;
References: <> <> <>
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100301 Fedora/3.0.3-1.fc12 Thunderbird/3.0.3
On 03/22/2010 06:30 PM, Zhuang Yuyao wrote:
Thanks for your reply. Will this issue be solved soon? Is it a
hardware issue or a software one?

A combination.  I think a Software fix is possible.

Can I make the 4G-256M memory
reserved so that kernel will not try to allocate memory in this area?

I have never tried it.

The issue is maintaining mappings for 32-bit PCI devices. If you only want to support 64-bit devices, it would be easier to address the issue.

David Daney

can not use more than 4G ram is bothersome since the memory is so cheap now. :-)

Thanks very much.

On Tue, Mar 23, 2010 at 12:44 AM, David Daney<>  wrote:

This is a known issue.

passing mem==3072M will restrict kernel memory usage thus avoiding the

David Daney

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