From: George Guo <[email protected]> QEMU places its machine FDT at physical address 0x100000 when booting with '-kernel'. KEXEC_CONTROL_CODE was defined at the same address, so machine_kexec_prepare() overwrites the FDT with the relocation trampoline before jumping to the new kernel.
The kexec'd kernel's fdt_setup() reads the FDT pointer from the EFI config table (FDTPTR = 0x100000) and finds trampoline code instead of a valid FDT, so earlycon auto-detection fails and the second kernel boots silently with no console output. Move KEXEC_CONTROL_CODE to 0x180000, which is still within the first 2MB reserved by memblock_init() and does not conflict with the QEMU FDT. Signed-off-by: George Guo <[email protected]> --- arch/loongarch/kernel/machine_kexec.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c index d7fafda1d541..44df7dbd3de5 100644 --- a/arch/loongarch/kernel/machine_kexec.c +++ b/arch/loongarch/kernel/machine_kexec.c @@ -21,8 +21,13 @@ #include <asm/cacheflush.h> #include <asm/page.h> -/* 0x100000 ~ 0x200000 is safe */ -#define KEXEC_CONTROL_CODE TO_CACHE(0x100000UL) +/* + * Both addresses are within the first 2MB which is always reserved by + * memblock_init(). Avoid 0x100000 because QEMU places its machine FDT + * there when using '-kernel'; overwriting it silences earlycon in the + * kexec'd kernel. + */ +#define KEXEC_CONTROL_CODE TO_CACHE(0x180000UL) #define KEXEC_CMDLINE_ADDR TO_CACHE(0x108000UL) static unsigned long reboot_code_buffer; -- 2.25.1
