[PATCH v4 0/4] kexec-tools, x86: E820 memmap pass for kdump

[WANG Chao]

Hi, Vivek

Sorry for my late response.

On 03/20/14 at 11:42am, Vivek Goyal wrote:
> On Wed, Mar 19, 2014 at 04:03:57PM +0800, WANG Chao wrote:
> > Hi, All
> > 
> > When kaslr comes in and kdump is broken, it seems about the right time to use
> > E820 instead of memmap=exactmap to pass memmap for kdump for the default memmap
> > passing mechanism:
> > http://lists.infradead.org/pipermail/kexec/2014-February/011048.html
> 
> What's the connection between kaslr and passing memory mappings in
> bootparams?

kaslr doesn't work with memmap=exactmap. kaslr happens before parsing
user defined memmap and it walks through E820 in boot_params to
determine 2nd kernel text area. And it would override the 1st kernel's
ram.

> 
> To me this is completely independent of kaslr. This is moving towards
> a better design to pass memory map to second kernel which in turn will
> also solve the issue of too many memory ranges on large machines.

Yes. You're right. That's what this patchset is mostly for.
kASLR is just one of the reasons.

> 
> Also, could you get hold of a machine with calgary IOMMU and test that
> --pass-memmap option makes those calgary machines work?

I couldn't find any calgary box. I tried to force calgary iommu on some
IBM-X series, but didn't work out. Those old hardwares are really hard
to find these days.

I think given the fact that the calgary code chage is simple enough and
hpa has committed to tip tree, this patchset won't risk much.

Thanks
WANG Chao