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Date: Thu, 30 Aug 2018 20:59:09 +0800 From: Feng Tang <feng.tang@...el.com> To: Michal Hocko <mhocko@...nel.org> Cc: Thomas Gleixner <tglx@...utronix.de>, Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org, x86@...nel.org, Ingo Molnar <mingo@...e.hu>, "H . Peter Anvin" <hpa@...ux.intel.com>, Yinghai Lu <yinghai@...nel.org>, Dave Hansen <dave.hansen@...el.com>, Andi Kleen <ak@...ux.intel.com> Subject: Re: [PATCH] x86, mm: Reserver some memory for bootmem allocator for NO_BOOTMEM On Thu, Aug 30, 2018 at 02:49:15PM +0200, Michal Hocko wrote: > On Thu 30-08-18 13:54:19, Thomas Gleixner wrote: > > On Thu, 30 Aug 2018, 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: > > > > > 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 > > > making earlycon depend on NO_BOOTMEM=n doesn't sound like a good fit to > > > > If we want to remove bootmem, then reintroducing it with a static bootmem > > section doesn't make any sense at all. > > I have actually checked the code now and see what you mean. I thought it > would be a single allocation that is needed but that is not the case so > the static buffer is not going to fly. Exactly! I tried several ways for the static allocation, like in data, in bss section, but they all failed, as in the very start of setup_arch(): memblock_reserve(__pa_symbol(_text), (unsigned long)__bss_stop - (unsigned long)_text); Those [_text, __bss_stop] is not able to be used by alloc_bootmem(). And I only got this patch, and really appreciate any good suggestions. Thanks, Feng
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