Re: [PATCH v2] x86/kexec: Exclude GART aperture from vmcore

[Baoquan He]

On 12/27/17 at 01:25pm, Borislav Petkov wrote:
> On Wed, Dec 27, 2017 at 03:44:49PM +0800, Baoquan He wrote:
> > > yes, instead of crashing the machine (because GART may be initialized in the
> > > 2nd kernel, overlapping the 1st kernel memory, which the 2nd kernel with its
> > > fake e820 map sees as unused).
> > > 
> > > I'd say this is an improvement.
> > 
> > I don't get what you said. If 'iommu=off' only specified in 1st kernel,
> > kdump kernel will think the memory which GART bar pointed as a hole.
> > This is incorrect. I don't see the improvement.
> 
> So he says, this memory is unused. Why is that incorrect?!?

'iommu=off' specified in 1st kernel, that region will be normal memory,
there could be important kernel data written into the place. While kdump
kernel will take that region as a gart aperture, trying to read data
from that region will cause error which Jiri originally tried to fix.