path: root/kernel/kexec.c
diff options
authorHuang Ying <ying.huang@intel.com>2008-07-25 19:45:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-26 12:00:04 -0700
commit89081d17f7bb81d89fa1aa9b70f821c5cf4d39e9 (patch)
tree1835fa64801fee048c8074ae4d63b0a7f4b14ee3 /kernel/kexec.c
parent3ab83521378268044a448113c6aa9a9e245f4d2f (diff)
kexec jump: save/restore device state
This patch implements devices state save/restore before after kexec. This patch together with features in kexec_jump patch can be used for following: - A simple hibernation implementation without ACPI support. You can kexec a hibernating kernel, save the memory image of original system and shutdown the system. When resuming, you restore the memory image of original system via ordinary kexec load then jump back. - Kernel/system debug through making system snapshot. You can make system snapshot, jump back, do some thing and make another system snapshot. - Cooperative multi-kernel/system. With kexec jump, you can switch between several kernels/systems quickly without boot process except the first time. This appears like swap a whole kernel/system out/in. - A general method to call program in physical mode (paging turning off). This can be used to invoke BIOS code under Linux. The following user-space tools can be used with kexec jump: - kexec-tools needs to be patched to support kexec jump. The patches and the precompiled kexec can be download from the following URL: source: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec-tools-src_git_kh10.tar.bz2 patches: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec-tools-patches_git_kh10.tar.bz2 binary: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec_git_kh10 - makedumpfile with patches are used as memory image saving tool, it can exclude free pages from original kernel memory image file. The patches and the precompiled makedumpfile can be download from the following URL: source: http://khibernation.sourceforge.net/download/release_v10/makedumpfile/makedumpfile-src_cvs_kh10.tar.bz2 patches: http://khibernation.sourceforge.net/download/release_v10/makedumpfile/makedumpfile-patches_cvs_kh10.tar.bz2 binary: http://khibernation.sourceforge.net/download/release_v10/makedumpfile/makedumpfile_cvs_kh10 - An initramfs image can be used as the root file system of kexeced kernel. An initramfs image built with "BuildRoot" can be downloaded from the following URL: initramfs image: http://khibernation.sourceforge.net/download/release_v10/initramfs/rootfs_cvs_kh10.gz All user space tools above are included in the initramfs image. Usage example of simple hibernation: 1. Compile and install patched kernel with following options selected: CONFIG_X86_32=y CONFIG_RELOCATABLE=y CONFIG_KEXEC=y CONFIG_CRASH_DUMP=y CONFIG_PM=y CONFIG_HIBERNATION=y CONFIG_KEXEC_JUMP=y 2. Build an initramfs image contains kexec-tool and makedumpfile, or download the pre-built initramfs image, called rootfs.gz in following text. 3. Prepare a partition to save memory image of original kernel, called hibernating partition in following text. 4. Boot kernel compiled in step 1 (kernel A). 5. In the kernel A, load kernel compiled in step 1 (kernel B) with /sbin/kexec. The shell command line can be as follow: /sbin/kexec --load-preserve-context /boot/bzImage --mem-min=0x100000 --mem-max=0xffffff --initrd=rootfs.gz 6. Boot the kernel B with following shell command line: /sbin/kexec -e 7. The kernel B will boot as normal kexec. In kernel B the memory image of kernel A can be saved into hibernating partition as follow: jump_back_entry=`cat /proc/cmdline | tr ' ' '\n' | grep kexec_jump_back_entry | cut -d '='` echo $jump_back_entry > kexec_jump_back_entry cp /proc/vmcore dump.elf Then you can shutdown the machine as normal. 8. Boot kernel compiled in step 1 (kernel C). Use the rootfs.gz as root file system. 9. In kernel C, load the memory image of kernel A as follow: /sbin/kexec -l --args-none --entry=`cat kexec_jump_back_entry` dump.elf 10. Jump back to the kernel A as follow: /sbin/kexec -e Then, kernel A is resumed. Implementation point: To support jumping between two kernels, before jumping to (executing) the new kernel and jumping back to the original kernel, the devices are put into quiescent state, and the state of devices and CPU is saved. After jumping back from kexeced kernel and jumping to the new kernel, the state of devices and CPU are restored accordingly. The devices/CPU state save/restore code of software suspend is called to implement corresponding function. Known issues: - Because the segment number supported by sys_kexec_load is limited, hibernation image with many segments may not be load. This is planned to be eliminated by adding a new flag to sys_kexec_load to make a image can be loaded with multiple sys_kexec_load invoking. Now, only the i386 architecture is supported. Signed-off-by: Huang Ying <ying.huang@intel.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: Nigel Cunningham <nigel@nigel.suspend2.net> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/kexec.c')
1 files changed, 39 insertions, 0 deletions
diff --git a/kernel/kexec.c b/kernel/kexec.c
index a0d920915b3..c8a4370e2a3 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -26,6 +26,10 @@
#include <linux/numa.h>
#include <linux/suspend.h>
#include <linux/device.h>
+#include <linux/freezer.h>
+#include <linux/pm.h>
+#include <linux/cpu.h>
+#include <linux/console.h>
#include <asm/page.h>
#include <asm/uaccess.h>
@@ -1441,7 +1445,31 @@ int kernel_kexec(void)
if (kexec_image->preserve_context) {
+ mutex_lock(&pm_mutex);
+ pm_prepare_console();
+ error = freeze_processes();
+ if (error) {
+ error = -EBUSY;
+ goto Restore_console;
+ }
+ suspend_console();
+ error = device_suspend(PMSG_FREEZE);
+ if (error)
+ goto Resume_console;
+ error = disable_nonboot_cpus();
+ if (error)
+ goto Resume_devices;
+ /* At this point, device_suspend() has been called,
+ * but *not* device_power_down(). We *must*
+ * device_power_down() now. Otherwise, drivers for
+ * some devices (e.g. interrupt controllers) become
+ * desynchronized with the actual state of the
+ * hardware at resume time, and evil weirdness ensues.
+ */
+ error = device_power_down(PMSG_FREEZE);
+ if (error)
+ goto Enable_irqs;
} else {
@@ -1459,7 +1487,18 @@ int kernel_kexec(void)
if (kexec_image->preserve_context) {
+ device_power_up(PMSG_RESTORE);
+ Enable_irqs:
+ enable_nonboot_cpus();
+ Resume_devices:
+ device_resume(PMSG_RESTORE);
+ Resume_console:
+ resume_console();
+ thaw_processes();
+ Restore_console:
+ pm_restore_console();
+ mutex_unlock(&pm_mutex);