Re: [PATCH] disable CPU side GART accesses

From: Bob Montgomery
Date: Thu Oct 16 2008 - 15:26:49 EST

On Thu, 2008-10-16 at 17:43 +0000, Yinghai Lu wrote:
> On Thu, Oct 16, 2008 at 10:00 AM, Bob Montgomery <bob.montgomery@xxxxxx> wrote:
> >
> > The problem occurs when the copy operation reads from the GART aperture
> > (iommu window) and wakes up the GART translation hardware. This patch
> > stops that by telling the GART to ignore addresses that come from the
> > CPU and to only translate addresses from the IO side.
> why kdump need to copy those area? those area is supposed to be
> reserved in e820 table by BIOS or first kernel.
> YH

The crashdump analysis tools do not need a copy of this area. But if a
user tool associated with the kdump operation manages to touch it
through /proc/vmcore or /dev/oldmem, it can crash the kdump kernel.
This seemed like a simple and logical way to prevent that danger.

Bob Montgomery

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