On Mon, Dec 27, 2010 at 04:13:55PM -0800, H. Peter Anvin wrote: > On 12/27/2010 04:06 PM, Vivek Goyal wrote: > > On Mon, Dec 27, 2010 at 12:31:20PM -0800, H. Peter Anvin wrote: > >> Hi guys, > >> > >> I'm planning a major overhaul of the trampoline allocation in x86, and > >> I'm trying to understand how kdump deals with it. The trampoline has to > >> be allocated in low memory (< 1 MiB) and obviously that doesn't include > >> the kdump area at all. > > > > Hi Peter, > > > > Kdump has the concept of backup area. We backup the contents of first > > 640KB of physical RAM in kdump reserved area and then allow kdump kernel > > to use first 640KB of memory. So any trampoline allocation can be done > > in low memory area without overwritting the contents of first kernel. > > > > OK, that's straightforward. That presumably means that the low 640K is > marked unused in the memory map that memblock sees during early startup. Yes, the available memory for second kernel is told to second kernel with kernel command line option "memmap=", hence it should be visible to memblock and it should be able to allocate this memory. Thanks Vivek
