Serge E. Hallyn wrote: > Quoting Oren Laadan ([email protected]): >> >> Serge E. Hallyn wrote: >>> Quoting Oren Laadan ([email protected]): >>>> Serge E. Hallyn wrote: >>>>> Quoting Oren Laadan ([email protected]): >>>>>> Serge E. Hallyn wrote: >>>>>>> Quoting Oren Laadan ([email protected]): >>>>>>>> Serge E. Hallyn wrote: >>>>>>>>> Quoting Oren Laadan ([email protected]): >>>>>>>>>> Cool ! >>>>>>>>>> >>>>>>>>>> So what do we have working now for 64 bit kernel (for 32 bit kernel >>>>>>>>>> we know it works...): >>>>>>>>>> >>>>>>>>>> 'restart' checkpointed >>>>>>>>>> program program >>>>>>>>>> ---------------------------------------- >>>>>>>>>> 64bit 64bit -> works >>>>>>>>>> 32bit 32bit -> works >>>>>>>>>> >>>>>>>>>> 64bit 32bit -> ????? >>>>> s/?????/Rejected/ >>>>> >>>>> CKPT_ARCH_ID is of course different for X86_32 than X86_64, so >>>>> we refuse restart in restore_read_header(). >>>>> >>>>> -serge >>>>> >>>> lol ... that's actually funny ! >>>> >>>> Anyway, in light of the IRC discussions, here are the cases again: >>>> >>>> >>>> original original restart target >>>> program kernel program kernel >>>> -------- --------- -------- -------- >>>> 64 bit 64 bit 64 bit 64 bit [0] works >>>> >>>> 32 bit 32 bit 32 bit 32 bit [0] works >>>> 32 bit 64 bit 32 bit 64 bit [0] works >>>> >>>> 32 bit 32 bit 32 bit 64 bit [1] >>>> 32 bit 64 bit 32 bit 32 bit [1] >>>> >>>> 32 bit any 64 bit 64 bit [2] >>>> 64 bit 64 bit 32 bit 64 bit [2] >>>> >>>> [0] The first 3 cases are "homogeneous", with conditions equal at >>>> checkpoint and restart. AFAIK, they work. >>>> >>>> [1] The next two cases consider 32 bit program, and vary only the >>>> environment - the kernel may change from 32 to 64 or back. We want >>>> them to work. >>>> >>>> IIUC, your comment above means that they don't work because the >>>> CKPT_ARCH_ID is a mismatch. The fix should be trivial - either >>>> make 'restart' modify it, or make the kernel tolerate it. ^^^^^^^^^^^^^^^^^^^^^^^^ ---->
>>> Well, you'd think so, but we also check for uts->machine, and want >>> to eventually check for kernel config, both of which are obviously >>> different. >> Then we'll have to take that in account when we get to also >> check those other fields. >> >>> After I comment out the obvious offending checks, it still fails to >>> restart from x8632->x86-64. I can spend some time next week figuring >>> out what we're not quite doing right as there shouldn't be a >>> problem really. But do we definately want to go out of our way to try >>> and mask out the differences in this case, while trying to detect >>> cpu differences between two x86-32's for instance? >> I agree, there shouldn't be a problem really, and I expect this to >> be a very useful feature for migration/fault-tolerance. > > May be, but then perhaps this is the first case where we should be > using a userspace checkpoing image rewriter to help us out. Otherwise > we'll need to hardcode in the kernel that a task which was > checkpointed on X86_32 should, on x86_64, have TIF_IA32 added to > the thread_flags but may be restarted; etc. Should be doable, but > kind of ugly... Indeed. I offered that path above :) Since we are going to need the bit-ness of a task for the tree creation as well, how about: 1) Add the bit-ness property to the pids_arr[], e.g. as a flags field (we may need use it for other stuff later). 2) 'restart' already examines and possibly modifies pids_arr[], so in transition from 32->64 it will add that flag, and in the opposite transition it will check/remove that flag. 3) 'restart' will also change the header architecture as needed. 4) The kernel will verify that the bitness reported in pids_arr[] is the same as the actual process. (This is just a sanity check, of course). Later we'll also make 'restart' use that bit-ness information to decide whether an exec() is needed to change own bit-ness. Oren. _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
