[PATCH] kho: check fdt_phys in is_kho_boot()

[Pratyush Yadav]

On Thu, Oct 22 2026, Greg Thelen wrote:

> During arm64 setup_arch(), efi_init() -> reserve_regions() calls
> is_kho_boot() before arm64_memblock_init() initializes memstart_addr.
> At this point memstart_addr still holds its initial sentinel value (-1).
>
> When booting via kexec with KHO enabled, kho_populate() sets
> kho_in.fdt_phys from the /chosen FDT node. Calling is_kho_boot() ->
> kho_get_fdt() invokes phys_to_virt(kho_in.fdt_phys), which evaluates
> PHYS_OFFSET and triggers VM_BUG_ON(memstart_addr & 1) on arm64 kernels
> built with CONFIG_DEBUG_VM=y:
>
>   kernel BUG at ./arch/arm64/include/asm/memory.h:377!
>   Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
>   Call trace:
>    is_kho_boot+0x2c/0x38 (P)
>    efi_init+0x94/0xf8
>    setup_arch+0xf0/0x240
>    start_kernel+0x84/0x490
>    __primary_switched+0x88/0x98
>
> Check kho_in.fdt_phys directly in is_kho_boot() instead of calling
> kho_get_fdt() so that early boot callers do not invoke phys_to_virt()
> before the linear map offset is initialized.
>
> Fixes: d6d511639185 ("kexec: introduce is_kho_boot()")
> Assisted-by: Gemini:gemini-3.8-flash
> Signed-off-by: Greg Thelen <gthelen at google.com>

Reviewed-by: Pratyush Yadav (Google) <pratyush at kernel.org>

[...]

-- 
Regards,
Pratyush Yadav