Re: [PATCH] x86, kdump: Set crashkernel_low automatically

[H. Peter Anvin]

On 03/11/2013 12:22 PM, Vivek Goyal wrote:
> 
> So always reserving memory at highest address will break all the cases
> which work without iommu and rely on swiotlb. I think first we need
> to make sure that kdump works reliably with iommu on, and then try
> to move to always reserving memory at higest possible address.
> 

We should clearly always reserve an swiotlb window, *or*, probably much
better, teach the kdump kernel to *make* an swiotlb window (by having a
memory buffer in its reserved memory area into which it copies a chunk
of low memory, just as we do for the bottom megabyte.  If we are already
in low memory that buffer becomes the swiotlb window, no copy necessary.)

	-hpa

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