Messages in this thread | | | Date | Mon, 11 Mar 2013 12:59:44 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] x86, kdump: Set crashkernel_low automatically |
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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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