Re: [PATCH 0/3 -mm] kexec jump -v8

[Vivek Goyal <vgoyal@redhat.com>]

On Thu, Dec 27, 2007 at 10:33:13AM +0800, Huang, Ying wrote:
> On Wed, 2007-12-26 at 20:57 -0500, Vivek Goyal wrote:
> [...]
> > > 9. Now, you are in the original kernel again. You can read/write the
> > >    memory image of kexeced kernel via /proc/kimgcore.
> > > 
> > 
> > Why do we need two interfaces, /proc/vmcore and /proc/kimgcore? Can't
> > we have just one say /proc/vmcore. Irrespective of what kernel you are
> > in /proc/vmcore gives you the access to the memory of kernel which was
> > previously booted.
> 
> In theory we can kexec another kernel even in a kexeced kernel, that is,
> in kernel A kexec kernel B, and in kernel B kexec another kernel C. In
> this situation, both /proc/vmcore and /proc/kimgcore has valid contents.
> So I think, it may be better to keep two interfaces.
> 

In those situations I think only one interface is better. For example, 
above will be broken if somebody kexec 4 kernels.

A-->B--->C--->D

I think better option might be if it is stack like situation. A kernel
shows you only the previous kernel's memory contents through /proc/vmcore
interface. So If I am in kernel D, I see only kernel C's memory image.
To see kernel B's memory image, one shall have to go back to kernel C.

Thanks
Vivek