In place kexec

David Woodhouse dwmw2 at
Fri Jul 30 14:50:19 EDT 2010

On Fri, 30 Jul 2010, Vivek Goyal wrote:

> On Fri, Jul 30, 2010 at 11:21:42AM -0700, Eric W. Biederman wrote:
>> David Woodhouse <dwmw2 at> writes:
>>> On Thu, 2010-07-29 at 21:41 -0700, Eric W. Biederman wrote:
>>>> There isn't a bus master shut off at the core level.
>>> Effectively, there is if you have an IOMMU.
>> Depends on the IOMMU.  There are several dinky IOMMUs that when you
>> shut them off DMA simply goes around them, and is not stopped.
> I think last time we were discussing this for AMD IOMMU where if you
> disable IOMMU, it just kind of become pass through with 1:1 mapping of
> addresses.

Yeah, don't do that. The IOMMU should be *on*, but without any active 
mappings set up. Which is exactly how Linux will set it up at boot.


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