Re: [PATCH 2/2] x86 e820: Introduce memmap=resetusablemap for kdump usage

H. Peter Anvin
2013-01-22T15:54:27Z

On 01/22/2013 09:20 AM, Thomas Renninger wrote:
> From: Yinghai Lu <yinghai@kernel.org>
>
> kdump voided the whole original e820 map and half way made
> it up via memmap= options passed via kdump boot params again.
>
> But this is conceptionally wrong. The whole original memory ranges
> which are declared reserved, ACPI data/nvs or however are not usable
> must stay the same and get honored by the kdump kernel.
>
> Therefore memmap=resetusablemap gets introduced.
> kdump passes this one and only the usable e820 ranges are removed.
> kdump passes the usable ranges to use via memmap=x@y parameter(s).
> The not usable e820 ranges are preserved.
>
> This for example fixes mmconf (extended PCI config access) and
> possibly other kernel parts which rely on remapped memory to be
> in reserved or ACPI (data/nvs) declared e820 memory areas.
>
> Tested-by: Thomas Renninger <trenn@suse.de>
> Reviewed-by: Thomas Renninger <trenn@suse.de>
> Signed-off-by: Thomas Renninger <trenn@suse.de>

Tested-by: and Reviewed-by: are rather redundant with Signed-off-by:.
Also, you should have a Signed-off-by: from the author (Yinghai).

However, when thinking about it this really doesn't seem to be the right
interface, either. Something like "memmap=reserveram" which turns all
RAM areas into reserved areas, which can then be overridden by memmap=
options would make more sense.

Even more sense would be to pass the modified memmap to kexec...

-hpa