($INBOX_DIR/description missing)
 help / color / mirror / Atom feed
From: Baoquan He <bhe@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, robh+dt@kernel.org,
	dan.j.williams@intel.com, nicolas.pitre@linaro.org,
	josh@joshtriplett.org, fengguang.wu@intel.com, bp@suse.de,
	andy.shevchenko@gmail.com, patrik.r.jakobsson@gmail.com,
	airlied@linux.ie, kys@microsoft.com, haiyangz@microsoft.com,
	sthemmin@microsoft.com, dmitry.torokhov@gmail.com,
	frowand.list@gmail.com, keith.busch@intel.com,
	jonathan.derrick@intel.com, lorenzo.pieralisi@arm.com,
	bhelgaas@google.com, tglx@linutronix.de, brijesh.singh@amd.com,
	jglisse@redhat.com, thomas.lendacky@amd.com,
	gregkh@linuxfoundation.org, baiyaowei@cmss.chinamobile.com,
	richard.weiyang@gmail.com, devel@linuxdriverproject.org,
	linux-input@vger.kernel.org, linux-nvdimm@lists.01.org,
	devicetree@vger.kernel.org, linux-pci@vger.kernel.org,
	ebiederm@xmission.com, vgoyal@redhat.com, dyoung@redhat.com,
	yinghai@kernel.org, monstr@monstr.eu, davem@davemloft.net,
	chris@zankel.net, jcmvbkbc@gmail.com, gustavo@padovan.org,
	maarten.lankhorst@linux.intel.com, seanpaul@chromium.org,
	linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
Subject: Re: [PATCH v7 4/4] kexec_file: Load kernel at top of system RAM if required
Date: Wed, 25 Jul 2018 14:48:13 +0800
Message-ID: <20180725064813.GI6480@MiWiFi-R3L-srv> (raw)
In-Reply-To: <20180723143443.GD18181@dhcp22.suse.cz>

On 07/23/18 at 04:34pm, Michal Hocko wrote:
> On Thu 19-07-18 23:17:53, Baoquan He wrote:
> > Kexec has been a formal feature in our distro, and customers owning
> > those kind of very large machine can make use of this feature to speed
> > up the reboot process. On uefi machine, the kexec_file loading will
> > search place to put kernel under 4G from top to down. As we know, the
> > 1st 4G space is DMA32 ZONE, dma, pci mmcfg, bios etc all try to consume
> > it. It may have possibility to not be able to find a usable space for
> > kernel/initrd. From the top down of the whole memory space, we don't
> > have this worry. 
> I do not have the full context here but let me note that you should be
> careful when doing top-down reservation because you can easily get into
> hotplugable memory and break the hotremove usecase. We even warn when
> this is done. See memblock_find_in_range_node

Kexec read kernel/initrd file into buffer, just search usable positions
for them to do the later copying. You can see below struct kexec_segment, 
for the old kexec_load, kernel/initrd are read into user space buffer,
the @buf stores the user space buffer address, @mem stores the position
where kernel/initrd will be put. In kernel, it calls
kimage_load_normal_segment() to copy user space buffer to intermediate
pages which are allocated with flag GFP_KERNEL. These intermediate pages
are recorded as entries, later when user execute "kexec -e" to trigger
kexec jumping, it will do the final copying from the intermediate pages
to the real destination pages which @mem pointed. Because we can't touch
the existed data in 1st kernel when do kexec kernel loading. With my
understanding, GFP_KERNEL will make those intermediate pages be
allocated inside immovable area, it won't impact hotplugging. But the
@mem we searched in the whole system RAM might be lost along with
hotplug. Hence we need do kexec kernel again when hotplug event is


struct kexec_segment {
         * This pointer can point to user memory if kexec_load() system
         * call is used or will point to kernel memory if
         * kexec_file_load() system call is used.
         * Use ->buf when expecting to deal with user memory and use ->kbuf
         * when expecting to deal with kernel memory.
        union {
                void __user *buf;
                void *kbuf;
        size_t bufsz;                                                                                                                             
        unsigned long mem;
        size_t memsz;

To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

  reply	other threads:[~2018-07-25  6:48 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-18  2:49 [PATCH v7 0/4] resource: Use list_head to link sibling resource Baoquan He
2018-07-18  2:49 ` [PATCH v7 1/4] resource: Move reparent_resources() to kernel/resource.c and make it public Baoquan He
2018-07-18  2:49 ` [PATCH v7 2/4] resource: Use list_head to link sibling resource Baoquan He
2018-07-18  2:49 ` [PATCH v7 3/4] resource: add walk_system_ram_res_rev() Baoquan He
2018-07-18  2:49 ` [PATCH v7 4/4] kexec_file: Load kernel at top of system RAM if required Baoquan He
2018-07-18 22:33   ` Andrew Morton
2018-07-19 15:17     ` Baoquan He
2018-07-19 19:44       ` Andrew Morton
2018-07-25  2:21         ` Baoquan He
2018-07-23 14:34       ` Michal Hocko
2018-07-25  6:48         ` Baoquan He [this message]
2018-07-26 12:59           ` Michal Hocko
2018-07-26 13:09             ` Baoquan He
2018-07-26 13:12               ` Michal Hocko
2018-07-26 13:14                 ` Michal Hocko
2018-07-26 13:37                   ` Baoquan He
2018-07-26 14:01                     ` Michal Hocko
2018-07-26 15:10                       ` Baoquan He

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180725064813.GI6480@MiWiFi-R3L-srv \
    --to=bhe@redhat.com \
    --cc=airlied@linux.ie \
    --cc=akpm@linux-foundation.org \
    --cc=andy.shevchenko@gmail.com \
    --cc=baiyaowei@cmss.chinamobile.com \
    --cc=bhelgaas@google.com \
    --cc=bp@suse.de \
    --cc=brijesh.singh@amd.com \
    --cc=chris@zankel.net \
    --cc=dan.j.williams@intel.com \
    --cc=davem@davemloft.net \
    --cc=devel@linuxdriverproject.org \
    --cc=devicetree@vger.kernel.org \
    --cc=dmitry.torokhov@gmail.com \
    --cc=dyoung@redhat.com \
    --cc=ebiederm@xmission.com \
    --cc=fengguang.wu@intel.com \
    --cc=frowand.list@gmail.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=gustavo@padovan.org \
    --cc=haiyangz@microsoft.com \
    --cc=jcmvbkbc@gmail.com \
    --cc=jglisse@redhat.com \
    --cc=jonathan.derrick@intel.com \
    --cc=josh@joshtriplett.org \
    --cc=keith.busch@intel.com \
    --cc=kexec@lists.infradead.org \
    --cc=kys@microsoft.com \
    --cc=linux-input@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-nvdimm@lists.01.org \
    --cc=linux-parisc@vger.kernel.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=lorenzo.pieralisi@arm.com \
    --cc=maarten.lankhorst@linux.intel.com \
    --cc=mhocko@kernel.org \
    --cc=monstr@monstr.eu \
    --cc=nicolas.pitre@linaro.org \
    --cc=patrik.r.jakobsson@gmail.com \
    --cc=richard.weiyang@gmail.com \
    --cc=robh+dt@kernel.org \
    --cc=seanpaul@chromium.org \
    --cc=sthemmin@microsoft.com \
    --cc=tglx@linutronix.de \
    --cc=thomas.lendacky@amd.com \
    --cc=vgoyal@redhat.com \
    --cc=yinghai@kernel.org \


* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

($INBOX_DIR/description missing)

This inbox may be cloned and mirrored by anyone:

	# this inbox consists of 2 epochs:
	git clone --mirror http://archive.lwn.net:8080/devicetree/0 devicetree/git/0.git	# oldest
	git clone --mirror http://archive.lwn.net:8080/devicetree/1 devicetree/git/1.git	# newest

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 devicetree devicetree/ http://archive.lwn.net:8080/devicetree \
		devicetree@vger.kernel.org lwn-devicetree@archive.lwn.net
	public-inbox-index devicetree

Example config snippet for mirrors.
Newsgroup available over NNTP:

AGPL code for this site: git clone https://public-inbox.org/public-inbox.git