Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756889Ab3JODBF (ORCPT ); Mon, 14 Oct 2013 23:01:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44395 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754206Ab3JODBE (ORCPT ); Mon, 14 Oct 2013 23:01:04 -0400 Date: Tue, 15 Oct 2013 11:00:18 +0800 From: WANG Chao To: Yinghai Lu Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Pekka Enberg , Jacob Shin , Andrew Morton , Vivek Goyal , "Eric W. Biederman" , "kexec@lists.infradead.org" , Linux Kernel Mailing List Subject: Re: [PATCH] x86, kdump: crashkernel=X try to reserve below 896M first, then try below 4G, then MAXMEM Message-ID: <20131015030018.GO18969@dhcp16-109.nay.redhat.com> References: <1381751200-27376-1-git-send-email-chaowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3382 Lines: 74 On 10/14/13 at 11:54am, Yinghai Lu wrote: > On Mon, Oct 14, 2013 at 4:46 AM, WANG Chao wrote: > > Now crashkernel=X will fail out if there's not enough memory at > > low (below 896M). What makes sense for crashkernel=X would be: > > > > - First try to reserve X below 896M (for being compatible with old > > kexec-tools). > > - If fails, try to reserve X below 4G (swiotlb need to stay below 4G). > > - If fails, try to reserve X from MAXMEM top down. > > > > So that user can easily reserve large memory with crashkernel=X instead > > of crashkernel=X,high. It's more transparent and user-friendly. > > > > If crashkernel is large and the reserved is beyond 896M, old kexec-tools > > won't be compatible with new kernel for most of time. > > > > kexec will fail out immediately in this case. But the failure could be > > expected, because old kexec users should not try to reserve that large > > amount of memory at the first place. > > > > On the other hand, old kexec also will fail on old kernel when there's > > not enough low memory to reserve a large crash kernel area. So the > > failure of old kexec is consistent between old kernel and new kernel. > > > > Signed-off-by: WANG Chao > > --- > > arch/x86/kernel/setup.c | 14 ++++++++++++++ > > 1 file changed, 14 insertions(+) > > > > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > > index f0de629..38e6c1f 100644 > > --- a/arch/x86/kernel/setup.c > > +++ b/arch/x86/kernel/setup.c > > @@ -593,6 +593,20 @@ static void __init reserve_crashkernel(void) > > high ? CRASH_KERNEL_ADDR_HIGH_MAX : > > CRASH_KERNEL_ADDR_LOW_MAX, > > crash_size, alignment); > > + /* > > + * crashkernel=X reserve below 896M fails? Try below 4G > > + */ > > + if (!high && !crash_base) > > + crash_base = memblock_find_in_range(alignment, > > + (1ULL << 32), > > + crash_size, alignment); > > + /* > > + * crashkernel=X reserve below 4G fails? Try MAXMEM > > + */ > > + if (!high && !crash_base) > > + crash_base = memblock_find_in_range(alignment, > > + CRASH_KERNEL_ADDR_HIGH_MAX, > > + crash_size, alignment); > > > > if (!crash_base) { > > pr_info("crashkernel reservation failed - No suitable area found.\n"); > > -- > > User should change crashkernel=X to crashkernel=X,high. crashkernel=X is more straightforward. IMHO, It should be a more general crash kernel reservation parameter and it shouldn't reserve at low only. > > As user could forget to update kexec-tools to utilize ",high" feature, and get > kdump later fail later. old kexec-tools should fail to load kernel high anyway, right? Thanks WANG Chao -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/