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[209.85.220.65]) by mx.google.com with SMTPS id k6sor14073795edx.3.2019.01.01.22.48.06 for (Google Transport Security); Tue, 01 Jan 2019 22:48:06 -0800 (PST) Received-SPF: pass (google.com: domain of kernelfans@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=WarTCNY0; spf=pass (google.com: domain of kernelfans@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=kernelfans@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=iLoKSSytsM+0SiOlGYwk8zox7JBE2gbCmO+/LdxPZBI=; b=WarTCNY0I1tvz/qfiEaFAMuW+gSYZLk/IB53c0yaTzJ6jqdJ5cDigPe2rx+E3zJWej xWJAlhg8wViBTYoWvz5CLfTKR+FvObPsG1SbSSCgxO3s94JCasx9zKnHNE3p+f4j+deZ zgnRk4loGqKbwUtFwsqGAKPWi5isaNByOGX3L5gwhDhH24M0HRjFeT7MgsPLFvKKmrtZ 8CH17sugvG0a1a2v0EtlXPWI3BALSRshQ/kg6pv9viDPF/UIi/BH8LfKs57nLez+vrIg 9BVGnZ/Akj780RwJ3lqkwBLLg09KMRLsmxK4+IGynwT9fX5UF68WUcKXrzR7Nu7TU2oj TV/g== X-Google-Smtp-Source: AFSGD/XZXAXwAjiL4nyx4K9YlpP4K/naYkkbRAKn9Prliikb0aoPOKwano0REdSuS6B+xVBAmgE/eSsWFPh37hKtNpg= X-Received: by 2002:a50:9feb:: with SMTP id c98mr38053176edf.253.1546411686136; Tue, 01 Jan 2019 22:48:06 -0800 (PST) MIME-Version: 1.0 References: <1545966002-3075-1-git-send-email-kernelfans@gmail.com> <1545966002-3075-3-git-send-email-kernelfans@gmail.com> <20181231084608.GB28478@rapoport-lnx> In-Reply-To: <20181231084608.GB28478@rapoport-lnx> From: Pingfan Liu Date: Wed, 2 Jan 2019 14:47:54 +0800 Message-ID: Subject: Re: [PATCHv3 2/2] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr To: Mike Rapoport Cc: linux-acpi@vger.kernel.org, linux-mm@kvack.org, kexec@lists.infradead.org, Tang Chen , "Rafael J. Wysocki" , Len Brown , Andrew Morton , Mike Rapoport , Michal Hocko , Jonathan Corbet , Yaowei Bai , Pavel Tatashin , Nicholas Piggin , Naoya Horiguchi , Daniel Vacek , Mathieu Malaterre , Stefan Agner , Dave Young , Baoquan He , yinghai@kernel.org, vgoyal@redhat.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Message-ID: <20190102064754.SvcXupRKcun4UzssPE9LF-BKrQAO6mYQgTTc-z9c9es@z> On Mon, Dec 31, 2018 at 4:46 PM Mike Rapoport wrote: > > On Fri, Dec 28, 2018 at 11:00:02AM +0800, Pingfan Liu wrote: > > Customer reported a bug on a high end server with many pcie devices, where > > kernel bootup with crashkernel=384M, and kaslr is enabled. Even > > though we still see much memory under 896 MB, the finding still failed > > intermittently. Because currently we can only find region under 896 MB, > > if w/0 ',high' specified. Then KASLR breaks 896 MB into several parts > > randomly, and crashkernel reservation need be aligned to 128 MB, that's > > why failure is found. It raises confusion to the end user that sometimes > > crashkernel=X works while sometimes fails. > > If want to make it succeed, customer can change kernel option to > > "crashkernel=384M, high". Just this give "crashkernel=xx@yy" a very > > limited space to behave even though its grammer looks more generic. > > And we can't answer questions raised from customer that confidently: > > 1) why it doesn't succeed to reserve 896 MB; > > 2) what's wrong with memory region under 4G; > > 3) why I have to add ',high', I only require 384 MB, not 3840 MB. > > > > This patch simplifies the method suggested in the mail [1]. It just goes > > bottom-up to find a candidate region for crashkernel. The bottom-up may be > > better compatible with the old reservation style, i.e. still want to get > > memory region from 896 MB firstly, then [896 MB, 4G], finally above 4G. > > > > There is one trivial thing about the compatibility with old kexec-tools: > > if the reserved region is above 896M, then old tool will fail to load > > bzImage. But without this patch, the old tool also fail since there is no > > memory below 896M can be reserved for crashkernel. > > > > [1]: http://lists.infradead.org/pipermail/kexec/2017-October/019571.html > > Signed-off-by: Pingfan Liu > > Cc: Tang Chen > > Cc: "Rafael J. Wysocki" > > Cc: Len Brown > > Cc: Andrew Morton > > Cc: Mike Rapoport > > Cc: Michal Hocko > > Cc: Jonathan Corbet > > Cc: Yaowei Bai > > Cc: Pavel Tatashin > > Cc: Nicholas Piggin > > Cc: Naoya Horiguchi > > Cc: Daniel Vacek > > Cc: Mathieu Malaterre > > Cc: Stefan Agner > > Cc: Dave Young > > Cc: Baoquan He > > Cc: yinghai@kernel.org, > > Cc: vgoyal@redhat.com > > Cc: linux-kernel@vger.kernel.org > > --- > > arch/x86/kernel/setup.c | 9 ++++++--- > > 1 file changed, 6 insertions(+), 3 deletions(-) > > > > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > > index d494b9b..165f9c3 100644 > > --- a/arch/x86/kernel/setup.c > > +++ b/arch/x86/kernel/setup.c > > @@ -541,15 +541,18 @@ static void __init reserve_crashkernel(void) > > > > /* 0 means: find the address automatically */ > > if (crash_base <= 0) { > > + bool bottom_up = memblock_bottom_up(); > > + > > + memblock_set_bottom_up(true); > > > > /* > > * Set CRASH_ADDR_LOW_MAX upper bound for crash memory, > > * as old kexec-tools loads bzImage below that, unless > > * "crashkernel=size[KMG],high" is specified. > > */ > > crash_base = memblock_find_in_range(CRASH_ALIGN, > > - high ? CRASH_ADDR_HIGH_MAX > > - : CRASH_ADDR_LOW_MAX, > > - crash_size, CRASH_ALIGN); > > + (max_pfn * PAGE_SIZE), crash_size, CRASH_ALIGN); > > + memblock_set_bottom_up(bottom_up); > > Using bottom-up does not guarantee that the allocation won't fall into a > removable memory, it only makes it highly probable. > > I think that the 'max_pfn * PAGE_SIZE' limit should be replaced with the > end of the non-removable memory node. > Since passing MEMBLOCK_NONE, memblock_find_in_range() ->...-> __next_mem_range(), there is a logic to guarantee hotmovable memory will not be stamped over. if (movable_node_is_enabled() && memblock_is_hotpluggable(m)) continue; Thanks, Pingfan > > + > > if (!crash_base) { > > pr_info("crashkernel reservation failed - No suitable area found.\n"); > > return; > > -- > > 2.7.4 > > > > -- > Sincerely yours, > Mike. >