+ Dave Young, which I accidentally missed in my initial post On Thu, 29 Apr 2021 14:35:31 +0100, Marc Zyngier <maz@xxxxxxxxxx> wrote: > > It recently became apparent that using kexec with kexec_file_load() on > arm64 is pretty similar to playing Russian roulette. > > Depending on the amount of memory, the HW supported and the firmware > interface used, your secondary kernel may overwrite critical memory > regions without which the secondary kernel cannot boot (the GICv3 LPI > tables being a prime example of such reserved regions). > > It turns out that there is at least two ways for reserved memory > regions to be described to kexec: /proc/iomem for the userspace > implementation, and memblock.reserved for kexec_file. And of course, > our LPI tables are only reserved using the resource tree, leading to > the aforementioned stamping. Similar things could happen with ACPI > tables as well. > > On my 24xA53 system artificially limited to 256MB of RAM (yes, it > boots with that little memory), trying to kexec a secondary kernel > failed every times. I can only presume that this was mostly tested > using kdump, which preserves the entire kernel memory range. > > This small series aims at triggering a discussion on what are the > expectations for kexec_file, and whether we should unify the two > reservation mechanisms. > > And in the meantime, it gets things going... > > Marc Zyngier (2): > firmware/efi: Tell memblock about EFI reservations > ACPI: arm64: Reserve the ACPI tables in memblock > > arch/arm64/kernel/acpi.c | 1 + > drivers/firmware/efi/efi.c | 23 ++++++++++++++++++++++- > 2 files changed, 23 insertions(+), 1 deletion(-) Any comment on this? I've separately started working on using the resource tree to slice and dice the memblocks that are candidate for kexec_file_load(), but I'd like some consensus on whether this is the right way to address the issue. Without something like this, kexec_file_load() is not usable on arm64, so I'm pretty eager to see the back of this bug. Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
