From: Mike Rapoport <rppt@linux.ibm.com>
To: Pingfan Liu <kernelfans@gmail.com>
Cc: linux-acpi@vger.kernel.org, linux-mm@kvack.org,
kexec@lists.infradead.org, Tang Chen <tangchen@cn.fujitsu.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Len Brown <lenb@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Michal Hocko <mhocko@suse.com>, Jonathan Corbet <corbet@lwn.net>,
Yaowei Bai <baiyaowei@cmss.chinamobile.com>,
Pavel Tatashin <pasha.tatashin@oracle.com>,
Nicholas Piggin <npiggin@gmail.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Daniel Vacek <neelx@redhat.com>,
Mathieu Malaterre <malat@debian.org>,
Stefan Agner <stefan@agner.ch>, Dave Young <dyoung@redhat.com>,
Baoquan He <bhe@redhat.com>,
yinghai@kernel.org, vgoyal@redhat.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCHv3 2/2] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr
Date: Mon, 31 Dec 2018 10:46:09 +0200 [thread overview]
Message-ID: <20181231084608.GB28478@rapoport-lnx> (raw)
In-Reply-To: <1545966002-3075-3-git-send-email-kernelfans@gmail.com>
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 <kernelfans@gmail.com>
> Cc: Tang Chen <tangchen@cn.fujitsu.com>
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: Len Brown <lenb@kernel.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
> Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: Daniel Vacek <neelx@redhat.com>
> Cc: Mathieu Malaterre <malat@debian.org>
> Cc: Stefan Agner <stefan@agner.ch>
> Cc: Dave Young <dyoung@redhat.com>
> Cc: Baoquan He <bhe@redhat.com>
> 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.
> +
> if (!crash_base) {
> pr_info("crashkernel reservation failed - No suitable area found.\n");
> return;
> --
> 2.7.4
>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2018-12-31 8:46 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-28 3:00 [PATCHv3 0/2] mm/memblock: reuse memblock bottom-up allocation style Pingfan Liu
2018-12-28 3:00 ` [PATCHv3 1/2] mm/memblock: extend the limit inferior of bottom-up after parsing hotplug attr Pingfan Liu
2018-12-31 8:40 ` Mike Rapoport
2019-01-02 6:47 ` Pingfan Liu
2019-01-02 9:27 ` Mike Rapoport
2019-01-02 10:18 ` Baoquan He
2019-01-02 17:05 ` Mike Rapoport
2019-01-03 18:47 ` Tejun Heo
2019-01-04 15:09 ` Mike Rapoport
2019-01-05 3:44 ` Baoquan He
2019-01-06 6:27 ` Mike Rapoport
2019-01-08 8:50 ` Baoquan He
2019-01-07 8:37 ` Pingfan Liu
2019-01-04 5:59 ` Pingfan Liu
2019-01-04 16:20 ` Mike Rapoport
2018-12-28 3:00 ` [PATCHv3 2/2] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr Pingfan Liu
2018-12-31 8:46 ` Mike Rapoport [this message]
2019-01-02 6:47 ` Pingfan Liu
2019-01-02 9:28 ` Mike Rapoport
2018-12-28 3:39 ` [PATCHv3 0/2] mm/memblock: reuse memblock bottom-up allocation style Baoquan He
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