Arm64 Crashkernel doesn't work with FLATMEM anymore

Catalin Marinas catalin.marinas at
Thu Jan 2 09:42:06 PST 2020

On Mon, Dec 23, 2019 at 10:24:57PM +0000, Saeed Karimabadi (skarimab) wrote:
> On 20/12/2019 11:52 AM  James Morse <james.morse> wrote:
> > On 17/12/2019 00:02, Saeed Karimabadi (skarimab) wrote:
> > > Crash dump  Kernel doesn't work with FLATMEM memory model since version 4.11.0-rc3 and it
> > Because of these nomap memblocks, I don't think kdump is isolated enough from the systems
> > memory map for the flatmem illusion to hold just because its kdump. You still need to
> > access firmware table that describe the system, as well as any memory that was reserved
> > with mechanisms like this. This exposes you to the platform's not-really-flatmem memory
> > layout.
> > 
> > I think the real fix here is to remove FLATMEM.
> For example is it possible to reduce the amount of memory SPARMEM is
> using for its internal data structures or to keep track of different
> memory zones? Or any other suggestion of reducing the total memory
> size for crash kernel ?

Can you change SECTION_SIZE_BITS to 29 or 28 in
arch/arm64/include/asm/sparsemem.h and see whether it makes a


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