On Fri, Dec 07, 2007 at 03:53:30PM +0000, Huang, Ying wrote: > This patch implements the functionality of jumping between the kexeced > kernel and the original kernel. > > 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. > > To support jumping without reserving memory. One shadow backup page > (source page) is allocated for each page used by new (kexeced) kernel > (destination page). When do kexec_load, the image of new kernel is > loaded into source pages, and before executing, the destination pages > and the source pages are swapped, so the contents of destination pages > are backupped. Before jumping to the new (kexeced) kernel and after > jumping back to the original kernel, the destination pages and the > source pages are swapped too. > > A jump back protocol for kexec is defined and documented. It is an > extension to ordinary function calling protocol. So, the facility > provided by this patch can be used to call ordinary C function in real > mode. > > A set of flags for sys_kexec_load are added to control which state are > saved/restored before/after real mode code executing. For example, you > can specify the device state and FPU state are saved/restored > before/after real mode code executing. > > The states (exclude CPU state) save/restore code can be overridden > based on the "command" parameter of kexec jump. Because more states > need to be saved/restored by hibernating/resuming. > [..] > > -#define KEXEC_ON_CRASH 0x00000001 > -#define KEXEC_ARCH_MASK 0xffff0000 > +#define KEXEC_ON_CRASH 0x00000001 > +#define KEXEC_PRESERVE_CPU 0x00000002 > +#define KEXEC_PRESERVE_CPU_EXT 0x00000004 > +#define KEXEC_SINGLE_CPU 0x00000008 > +#define KEXEC_PRESERVE_DEVICE 0x00000010 > +#define KEXEC_PRESERVE_CONSOLE 0x00000020 Hi, Why do we need so many different flags for preserving different types of state (CPU, CPU_EXT, Device, console) ? To keep things simple, can't we can create just one flag KEXEC_PRESERVE_CONTEXT, which will indicate any special action required for preserving the previous kernel's context so that one can swith back to old kernel? Thanks Vivek _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
