linux-kernel - Re: How to make mmap'ed kernel buffer non-cacheable

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Message-ID: <6278d2220704200632p3300a6e2y8c9d14f4d735015c@mail.gmail.com>
Date:	Fri, 20 Apr 2007 14:32:41 +0100
From:	"Daniel J Blueman" <daniel.blueman@...il.com>
To:	bhuvan.mittal@...com
Cc:	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: How to make mmap'ed kernel buffer non-cacheable

On 20 Apr, 14:20, Bhuvan Kumar MITTAL <bhuvan.mit...@...com> wrote:
> Hi,
>   I am working on an audio device driver development on Linux. I have a kernel
> buffer which I have mapped to user space using mmap call from user space. My
> problem is that the data which comes to the kernel buffer is getting dropped in
> user space and I get only 50-60% of the data which is randomly ordered. The user
> to kernel level buffer address translation code is fine and I suspect this data
> dropping is occurring coz the kernel buffer is cacheable. Please suggest me some
> way of making the entire buffer non cacheable. I am stuck on this for quite a while
> now.

You can use rdmsr() in your driver to check if the page attribute
table MSR is available, then find and/or add the right entry in the
table to set in each page's flags. This is documented in the Intel
IA-32 Intel Architecture Software Developer's Manuals at intel.com.

Dan
-- 
Daniel J Blueman
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