x86/kdump: crashkernel=X try to reserve below 896M first then below 4G and MAXMEM

[Dave Young]

On 10/21/17 at 12:20am, Yinghai Lu wrote:
> On Thu, Oct 19, 2017 at 10:52 PM, Dave Young <dyoung at redhat.com> wrote:
> > Now crashkernel=X will fail if there's not enough memory at low region
> > (below 896M) when trying to reserve large memory size.  One can use
> > crashkernel=xM,high to reserve it at high region (>4G) but it is more
> > convinient to improve crashkernel=X to:
> >
> >  - First try to reserve X below 896M (for being compatible with old
> >    kexec-tools).
> >  - If fails, try to reserve X below 4G (swiotlb need to stay below 4G).
> >  - If fails, try to reserve X from MAXMEM top down.
> >
> > It's more transparent and user-friendly.
> 
> ok with me.

Thank you!

> 
> But looks like last time Vivek did not like this idea.

>From the old discussion I remember Vivek was fine with this patch:
https://lkml.org/lkml/2013/10/15/601

Thanks
Dave