"H. Peter Anvin" <hpa at zytor.com> writes: > 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. > That fits very cleanly with the patches I'm doing. Additionally we typically start with maxcpus=1 so we don't strictly need the trampoline to start other cpus. Eric
