Paolo Bonzini <pbonz...@redhat.com> writes: > On 09/12/2015 23:18, Bandan Das wrote: >> Commit a2b9e6c1a35afcc09: >> >> KVM: x86: Don't report guest userspace emulation error to userspace >> >> Commit fc3a9157d314 ("KVM: X86: Don't report L2 emulation failures to >> user-space") disabled the reporting of L2 (nested guest) emulation >> failures to >> userspace due to race-condition between a vmexit and the instruction >> emulator. >> The same rational applies also to userspace applications that are >> permitted by >> the guest OS to access MMIO area or perform PIO. >> >> This patch extends the current behavior - of injecting a #UD instead of >> reporting it to userspace - also for guest userspace code. >> >> I searched the archives but failed in finding anything. Can someone please >> explain why this is needed ? Or, why not let userspace decide what to do >> based >> on the cpl, whether to continue execution or kill the guest ? Is the >> assumption >> here that this is what userspace always wants ? > > Not what userspace always wants, but what the guest kernel always wants.
Thanks Paolo, this one I agree. > Allowing userspace to stop the guest with an emulation failure is a This one I don't :) Userspace started the guest after all, there are other ways for it to kill the guest if it wanted to. > possible denial of service, similar to L2 stopping L1 with an emulation > failure. > > Paolo > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html