On 29/08/14 09:37, Stefan Bader wrote: > On 29.08.2014 00:42, Andrew Cooper wrote: >> On 28/08/2014 19:01, Stefan Bader wrote: >>>>> So not much further... but then I think I know what I do next. Probably >>>>> should >>>>> have done before. I'll replace the WARN_ON in vmalloc that triggers by a >>>>> panic >>>>> and at least get a crash dump of that situation when it occurs. Then I >>>>> can dig >>>>> in there with crash (really should have thought of that before)... >>>> <nods> I dug a bit in the code (arch/x86/xen/mmu.c) but there is nothing >>>> there >>>> that screams at me, so I fear I will have to wait until you get the crash >>>> and get some clues from that. >>> Ok, what a journey. So after long hours of painful staring at the code... >>> (and btw, if someone could tell me how the heck one can do a mfn_to_pfn >>> in crash, I really would appreaciate :-P) >> The M2P map lives in the Xen reserved virtual address space in each PV >> guest, and forms part of the PV ABI. It is mapped read-only, in the >> native width of the guest. >> >> 32bit PV (PAE) at 0xF5800000 >> 64bit PV at 0xFFFF800000000000 >> >> This is represented by the MACH2PHYS_VIRT_START symbol from the Xen >> public header files. You should be able to blindly construct a pointer >> to it (if you have nothing better to hand), as it will be hooked into >> the guests pagetables before execution starts. Therefore, >> "MACH2PHYS_VIRT_START[(unsigned long)pfn]" ought to do in a pinch. > machine_to_phys_mapping is set to that address but its not mapped inside the > crash dump. Somehow vtop in crash handles translations. I need to have a look > at > their code, I guess. > > Thanks, > Stefan
What context is the crash dump? If it is a Xen+dom0 kexec()d to native linux, then the m2p should still be accessible given dom0's cr3. If it is some state copied off-host then you will need to adjust the copy to include that virtual range. ~Andrew -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
