On Sat, 2007-07-14 at 21:16 +0200, Rafael J. Wysocki wrote: > > The devices should be quiesced and the state of devices should be saved > > in kexec_jump, before relocate_kernel is called. This needs the > > implementation of device hibernating as you mentioned before. > > Hmm, at which point devices are normally shut down when kexec is used? I think putting devices in quiescent state (not in low power state) is sufficient for booting a new kernel with kexec, is it? According to my experiment, the new kernel can be booted with kexec if the .suspend method the drivers is called before kexec (given CONFIG_ACPI is not selected). Do we need a device quiesce/save + device shutdown for kexeced kernel to work? I don't think so. > > > > 4. In relocate_kernel, 0~16M is backupped firstly, then the > > > > hibernating kernel and initramfs is copied to 0~16M, after that, > > > > the hibernating kernel is booted. > > > > 5. In hibernating kernel, the memory of normal kernel (it is in > > > > 16M~512M) is saved into a hibernation image through /dev/mem > > > > and ELF header. > > > > > > I don't think it can be _that_ simple: > > > (a) what about processes' memory > > > (b) what about areas that shouldn't be saved? > > > > The mem_map (struct page[]) of every zone of hibernated kernel is > > checked. Necessary pages are saved, like memory snapshot of software > > suspend, but in user space. > > Well, it's not enough to check that, sorry. That's why we have > register_nosave_region(). After some investigation, I found the usage of "nosave" is as follow on i386: 1. __nosavedata used only for global variable in_suspend and swsusp_pg_dir 2. PG_nosave page flags used for snapshot itself Both are not necessary for kexec based hibernation. Because the image are written from a different kernel, the memory of hibernating kernel will not be saved, they can be used freely during image writing/reading. On x86_64, there is another usage of nosave during processing E820 memory map. But I don't know why the memory region other than E820_RAM are marked as nosave. I think only the memory region of type E820_RAM will be thought of normal memory, others will be thought as reserved. Is it sufficient just to check whether the page is reserved? Best Regards, Huang Ying _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
