On 29.08.2014 16:19, Andrew Cooper wrote: > 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.
No its a domU dump of a PV guest taken with "xl dump-core" (or actually the result of on-crash trigger). > > ~Andrew >
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