Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756570Ab3JNSyY (ORCPT ); Mon, 14 Oct 2013 14:54:24 -0400 Received: from mail-ie0-f181.google.com ([209.85.223.181]:64190 "EHLO mail-ie0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750884Ab3JNSyW (ORCPT ); Mon, 14 Oct 2013 14:54:22 -0400 MIME-Version: 1.0 In-Reply-To: <1381751200-27376-1-git-send-email-chaowang@redhat.com> References: <1381751200-27376-1-git-send-email-chaowang@redhat.com> Date: Mon, 14 Oct 2013 11:54:22 -0700 X-Google-Sender-Auth: 0FaN0PzeNZ6tRDTI57hACaViqPs Message-ID: Subject: Re: [PATCH] x86, kdump: crashkernel=X try to reserve below 896M first, then try below 4G, then MAXMEM From: Yinghai Lu To: WANG Chao 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 Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3001 Lines: 66 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. As user could forget to update kexec-tools to utilize ",high" feature, and get kdump later fail later. Yinghai -- 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/