On 01/12/2012 11:07 AM, Nadav Amit wrote: > >> > >> When I cleaned up insn_fetch(), I thought that fetching the instruction > >> which is being executed by the guest cannot cause #PF. > >> > >> The possibility that a meaningless userspace might similtaneously unmap > >> the page, noted by Avi IIRC, was ignored intentionally, so we just fail > >> in such a case. > >> > >> Did you see any real problem? > > Well, I run some research project for which I emulate instructions quite > often. I do see a real problem with Linux 3.0.0. Please note AFAIK #GP > might occur as well during instruction fetch. I don't think failing is the > right behavior in such case - there is no real reason to fail. > > Please tell me whether you are OK with KVM failing in such a scenario. So long as it's just the guest who is affected (at the same privilege level; we don't want guest userspace to cause a host failure). We might have issues with userspace causing such a failure, or a nested guest. I see we already check for that in handle_emulation_failure() (but not userspace). > If not - I'll send an updated patch (in which x86_decode_insn returns > EMULATION_OK when rc == X86EMUL_PROPAGATE_FAULT). It guess it's better to be correct in the emulator than rely on a failure allowing for guest-internal DoS. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
