On Thu, Aug 30, 2018 at 01:12:07PM +0200, Michal Hocko wrote: > On Thu 30-08-18 12:44:02, Peter Zijlstra wrote: > > 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. > > Well, there is endeavor to remove bootmem allocator altogether. So
wasn't aware of that. why? > making earlycon depend on NO_BOOTMEM=n doesn't sound like a good fit to > me. I am not familiar with this code path but why cannot we postpone the > allocation to later or use a statically allocated storage? because 'early'... I suppose. Youu really want the early con up and running asap.
