[PATCH 2/4] riscv: Add support for kexec handover (KHO)

[Chen Pei]

> [Severity: High]
> Can enabling ARCH_SUPPORTS_KEXEC_HANDOVER trigger a BUG_ON() in
> linear_mapping_pa_to_va() during efi_init() when booting a KHO kexec
> kernel on a 64-bit RISC-V UEFI system?

Confirmed. Reproduced on qemu virt booting through edk2 with
DEBUG_VIRTUAL enabled and "kho=on" on the outgoing kernel: the first
handover dies in the incoming one during EFI setup, before the console
registers, so it stays silent without an earlycon.

This will be fixed in v2.

> [Severity: Medium]
> Also, will kho_reserve_bootmem() fail on 64-bit RISC-V platforms
> where DRAM starts at or above 4 GiB, or record a 0-byte region when
> all DRAM lies below 4 GiB?

Confirmed, both halves. That is generic KHO code, not the riscv
enablement, so I will send a separate patch for it.

Best regards,
Chen