Re: In place kexec

Vivek Goyal
2010-07-30T18:56:25Z

On Fri, Jul 30, 2010 at 07:50:19PM +0100, David Woodhouse wrote:
> 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.
>

So what happens if we tear down the mapping while DMA is on.

Vivek