On Fri, Dec 21, 2007 at 03:33:19PM +0800, Huang, Ying wrote: > This patchset provides an enhancement to kexec/kdump. It implements > the following features: > > - Backup/restore memory used both by the original kernel and the > kexeced kernel. > > - Jumping between the original kernel and the kexeced kernel. > > - Read/write memory image of the kexeced kernel in the original kernel > and write memory image of the original kernel in the kexeced > kernel. This can be used as a communication method between the > kexeced kernel and the original kernel. > > > The features of this patchset can be used as follow: > > - Kernel/system debug through making system snapshot. You can make > system snapshot, jump back, do some thing and make another system > snapshot. > How do you differentiate between whether a core is resumable or not. IOW, how do you know the generated /proc/vmcore has been generated after a real crash hence can't be resumed (using krestore) or it has been generated because of hibernation/debug purposes and can be resumed? I think you might have to add an extra ELF NOTE to vmcore which can help decide whether kernel memory snapshot is resumable or not. [..] > 2. Build an initramfs image contains kexec-tool, or download the > pre-built initramfs image, called rootfs.gz in following text. > > 3. Boot kernel compiled in step 1. > > 4. Load kernel compiled in step 1 with /sbin/kexec. If You want to use > "krestore" tool, the --elf64-core-headers should be specified in > command line of /sbin/kexec. The shell command line can be as > follow: > > /sbin/kexec --load-jump-back /boot/bzImage --mem-min=0x100000 > --mem-max=0xffffff --elf64-core-headers --initrd=rootfs.gz > How about a different name like "--load-preserve-context". This will just mean that kexec need to preserve the context while kexeing to image being loaded. Combination of --load-jump-back and --load-jump-back-helper is becoming little confusing. > 5. Boot the kexeced kernel with following shell command line: > > /sbin/kexec -e > > 6. The kexeced kernel will boot as normal kexec. In kexeced kernel the > memory image of original kernel can read via /proc/vmcore or > /dev/oldmem, and can be written via /dev/oldmem. You can > save/restore/modify it as you want to. > Restoring a hibernated image using /dev/oldmem should be easy and I think one should be able to launch it back using --load-jump-back-helper. How do you restore already kexeced kernel? For example if I got two kernels A and B. A is the one which will hibernate and B will be used to store the hibernated kernel. I think as per the procedure one needs to first boot into kernel B and then jump back to kernel A. This will make image of B available in /proc/kimgcore. If I save /proc/kimgcore to disk and want to jump back to it, how do I do it? I guess I need to kexec again using --load-jump-back and not restore using krestore? > 7. Prepare jumping back from kexeced kernel with following shell > command lines: > > jump_back_entry=`cat /proc/cmdline | tr ' ' '\n' | grep kexec_jump_back_entry | cut -d '='` > /sbin/kexec --load-jump-back-helper=$jump_back_entry > How about decoupling entry point from --load-jump-back-helper. We can introduce a separate option for entry point. Something like. kexec --load-jump-back-helper --entry=$jump_back_entry May be we can generalize the --entry so that a user can override the entry point of the normal kexec image using above. > 8. Jump back to the original kernel with following shell command line: > > /sbin/kexec -e > > 9. Now, you are in the original kernel again. You can read/write the > memory image of kexeced kernel via /proc/kimgcore. > > 10. You can jump between the original kernel and kexeced kernel as you > want to via the following shell command line: > > /sbin/kexec -e > > > Known issues: > > - The suspend/resume callback of device drivers are used to put > devices into quiescent state. This will unnecessarily (possibly > harmfully) put devices into low power state. This is intended to be > solved by separating device quiesce/unquiesce callback from the > device suspend/resume callback. > > > ChangeLog: > > v8: > > - Split kexec jump patchset from kexec based hibernation patchset. > > - Add writing support to kimgcore. This can be used as a communication > method between kexeced kernel and original kernel. > What are we communicating between two kernels using kimgcore? I am setting up a system to test out the patches. More later... Thanks Vivek _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
