Re: [PATCH] x86/kexec: always ensure EFI systab region is mapped

[Dave Young]

On 04/23/19 at 06:20am, Junichi Nomura wrote:
> On 4/22/19 6:28 PM, Kairui Song wrote:
> > The reason is the systab region is not mapped by the identity mapping
> > provided by kexec. Currently kexec only create identity mapping for
> > mem regions, wihch won't cover the systab. So second kernel will be
> > accessing a not mapped memory region and cause fault.
> > But as kexec tend to pad the map region up to PUD size, the
> > systab could be included in the map by accident, so it worked on
> > some machines, but that will be broken easily and unstable.
> 
> Is the mapping of ACPI tables just by luck, too?

Hmm, guess it should be mapped by luck, here is the range on the T420: 
da99f000 - dae9efff Reserved (efi systab fall in this region)
daf9f000 - daffefff ACPI tables

Thanks
Dave