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

H. Peter Anvin
2013-01-29T01:11:43Z

On 01/28/2013 05:05 PM, Thomas Renninger wrote:
>
> But this (converting usable memory to reserved one before usable kdump memory
> is added) will let machines run into problems again for which the check:
> "mmconf area must be in reserved memory" got added?
>
> If, then memory which was usable before has to be converted to a special
> E820_KUMP (or whatever type) to make sure existing checks which look for
> "is reserved memory" still work the same way as in a productive kernel.
>
> Advantage of this would be that the info what originally was usable
> memory is preserved and can be used in future kdump related patches.
>
> So I guess the final patch should be:
> - Add a new e820 type:
> E820_KDUMP_RESERVED /* Originally usable memory where the crashed
> kernel kernel resided in */
> - Use Yinghai's last posted patch, but instead of:
> + e820_update_range(0, ULLONG_MAX, E820_RAM,
> + E820_RESERVED);
> ...
> + e820_remove_range(start_at, mem_size, E820_RESERVED, 0);
> do:
> + e820_update_range(0, ULLONG_MAX, E820_RAM,
> + E820_KDUMP_RESERVED);
> ...
> + e820_remove_range(start_at, mem_size, E820_KDUMP_RESERVED, 0);
>
> - Come up with another memmap=kdump_reserve_ram memmap option name
> or however it should get named...
>
> If this proposal gets accepted, I can send a tested patch...
>

Yes, this is much saner. There really shouldn't need to be an option,
even; since the tools need to be modified anyway, just modify the actual
memory map data structure itself.

-hpa