On 9/21/07, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > On Friday, 21 September 2007 05:33, Eric W. Biederman wrote: > > Nigel Cunningham <nigel@xxxxxxxxxxxxxxxxxx> writes: > > > > > > That's not true. Kexec will itself be an implementation, otherwise you'd end > > > up with people screaming about no hibernation support. > > > > There needs to be an implementation of hibernation based on kexec with > > return yes. > > > > > And it won't result in > > > the complete removal of the existing hibernation code from the kernel. At the > > > very least, it's going to want the kernel being hibernated to have an > > > interface by which it can find out which pages need to be saved. > > > > That interface should be running kernel -> user space -> target kernel. > > Not direct kernel to kernel. > > > > > I wouldn't > > > be surprised if it also ends up with an interface in which the kernel being > > > hibernated tells it what bdev/sectors in which to save the image as well > > > (otherwise you're going to need a dedicated, otherwise untouched partition > > > exclusively for the kexec'd kernel to use), or what network settings to use > > > if it wants to try to save the image to a network storage device. > > > > initramfs. We already seem to have that interface. And distros > > seems to do a pretty decent job of using it to configure systems. > > > > > On top of > > > that, there are all the issues related to device reinitialisation and so on, > > > > Yes. > > > > > and it looks like there's greatly increased pain for users wanting to > > > configure this new implementation. > > > > Not to be callous but that really is a user space and distro issue. > > > > > Kexec is by no means proven to be the panacea for all the issues. > > > > I agree. I'm still not quite convinced it will do a satisfactory job. > > But I think it does make sense to implement a general kexec with > > return and see if that can reasonably be used for handling hibernation > > issues. If done cleanly and with care the implementation won't be > > hibernation specific. > > Yes, and that's worth doing anyway, IMO. > > > Frankly this looks like the best way I can see to implement a general > > mechanism for calling silly firmware/BIOS/EFI services after we > > have a kernel up and running. It's a little bit like allowing > > X to call iopl(3) and do inb/outb directly. > > > > The configuration issues you raise pretty much exist for kexec on > > panic, and they seem to be being resolved for that case in a > > reasonable way. I do agree that the current kexec+return effort seems > > to be one of those unfortunate cases where we give every mechanism in > > the kernel to do something in user space and then no one actually > > implements the user space. That doesn't do any one any good. > > > > For hibernation we don't have the absolute need to step outside of the > > current kernel that we do in the kexec on panic approach. However we > > have this practical fight about mechanism and policy, and kexec with > > return has this seductive allure that it appears to be the minimal > > necessary mechanism in the kernel. > > > > No one has yet attacked the hard problem of coming up with separate > > hibernate methods for drivers. > > Well, I've been playing a bit with that for some time, but it's not easy by any > means. > > In short, I'm seeing some problems related to the handling of ACPI that seem to > shatter the entire idea of having separate hibernate methods, at least as far > as ACPI systems are concerned. So sadly to hear this. Can you details it a little? Or a link? Best Regards, Huang Ying _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
