On 2014-06-29 08:46, Gleb Natapov wrote: > On Sat, Jun 28, 2014 at 01:44:31PM +0200, Borislav Petkov wrote: >> qemu-system-x86-20240 [006] ...1 9406.484134: kvm_page_fault: address 7fffb62ba318 error_code 2 >> qemu-system-x86-20240 [006] ...1 9406.484136: kvm_inj_exception: #PF (0x2)a >> >> kvm injects the #PF into the guest. >> >> qemu-system-x86-20240 [006] d..2 9406.484136: kvm_entry: vcpu 1 >> qemu-system-x86-20240 [006] d..2 9406.484137: kvm_exit: reason PF excp rip 0xffffffff8161130f info 2 7fffb62ba318 >> qemu-system-x86-20240 [006] ...1 9406.484138: kvm_page_fault: address 7fffb62ba318 error_code 2 >> qemu-system-x86-20240 [006] ...1 9406.484141: kvm_inj_exception: #DF (0x0) >> >> Second #PF at the same address and kvm injects the #DF. >> >> BUT(!), why? >> >> I probably am missing something but WTH are we pagefaulting at a >> user address in context_switch() while doing a lockdep call, i.e. >> spin_release? We're not touching any userspace gunk there AFAICT. >> >> Is this an async pagefault or so which kvm is doing so that the guest >> rip is actually pointing at the wrong place? >> > There is nothing in the trace that point to async pagefault as far as I see. > >> Or something else I'm missing, most probably... >> > Strange indeed. Can you also enable kvmmmu tracing? You can also instrument > kvm_multiple_exception() to see which two exception are combined into #DF. > FWIW, I'm seeing the same issue here (likely) on an E-450 APU. It disappears with older KVM (didn't bisect yet, some 3.11 is fine) and when patch-disabling the vmport in QEMU. Let me know if I can help with the analysis. Jan
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