On Wed, 2008-06-11 at 12:30 -0400, Vivek Goyal wrote:[...]> > 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> > > > 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.> > > > One of the concerns raised by hibernation people in the past was to use> single boot loader entry to boot normally as well while resuming a kernel.> > So in this case a user either needs to maintain two boot-loader entries> or modify it on the fly. I wished there was a better way to handle that.
Now it is not needed to have two boot-loader entries, just one isenough. Step 4 and step 8 can share the same boot-loader entries. Therootfs.gz can be the normal initramfs or initrd when deployment. Inrootfs.gz, if there is a valid hibernation image, the hibernated systemwill be restored, otherwise, normal boot process follows.
> I am more interested in ability to have multiple kernel loaded in RAM> and capability to switch between them. Allows me to take non-disruptive> core dumps and somebody wanted to snapshots the kernels. That should> still work.> > > [..]> > --- a/arch/x86/kernel/machine_kexec_32.c> > +++ b/arch/x86/kernel/machine_kexec_32.c> > @@ -125,6 +125,12 @@ void machine_kexec(struct kimage *image)> > /* Interrupts aren't acceptable while we reboot */> > local_irq_disable();> > > > + if (image->preserve_context) {> > +#ifdef CONFIG_X86_IO_APIC> > + disable_IO_APIC();> > +#endif> > I think it would be a good idea to put some kind of comment here. We> need to put APICs in legacy mode so that we can get timer interrupts> in second kernel. kexec/kdump paths already have calls to> disable_IO_APIC() in one form or other. kexec jump path also needs one.
OK. I will add it.
Best Regards,Huang Ying
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