Re: In place kexec

David Woodhouse
2010-07-30T18:50:19Z

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@infradead.org> 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.

--
dwmw2