On Thu, Aug 30, 2018 at 05:03:19PM +0800, Feng Tang wrote: > We hit a kernel panic when enabling earlycon for a platform, the > call trace is: > > panic+0xd2/0x220 > __alloc_bootmem+0x31/0x34 > spp_getpage+0x60/0x8a > fill_pte+0x71/0x130 > __set_pte_vaddr+0x1d/0x50 > set_pte_vaddr+0x3c/0x60 > __native_set_fixmap+0x23/0x30 > native_set_fixmap+0x30/0x40 > setup_earlycon+0x1e0/0x32f > param_setup_earlycon+0x13/0x22 > do_early_param+0x5b/0x90 > parse_args+0x1f7/0x300 > parse_early_options+0x24/0x28 > parse_early_param+0x65/0x73 > setup_arch+0x31e/0x9f1 > start_kernel+0x58/0x44e > > The root cause is that when CONFIG_NO_BOOTMEM=y, before > e820__memblock_setup() is called there is no memory for bootmem > to allocate,
Which you bloody well asked for by using NO_BOOTMEM=y. Going down this route; adding hacks for every little thing that does want bootmem, completely defeats the purpose. If anything, make the earlycon thing depend on NO_BOOTMEM=n. That also solves your problem. No earlycon, no panic.
