On Sun, Feb 14, 2010 at 11:26:31AM +0100, Jan Kiszka wrote: > Gleb Natapov wrote: > > On Sat, Feb 13, 2010 at 10:31:12AM +0100, Jan Kiszka wrote: > >> From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> > >> > >> We intercept #BP while in guest debugging mode. As VM exists due to > >> intercepted exceptions do not necessarily come with valid > >> idt_vectoring, we have to update event_exit_inst_len explicitly in such > >> cases. At least in the absence of migration, this ensures that > >> re-injections of #BP will find and use the correct instruction length. > >> > > event_exit_inst_len is only used for event reinjection. Since event > > intercepted here will not be reinjected why updating event_exit_inst_len > > is needed here? > > In guest debugging mode a #BP exception is always reported to user space > to find out what caused it. If it was the guest itself, the exception is > reinjected, on older kernels via KVM_SET_GUEST_DEBUG and since 2.6.33 > via KVM_SET_VCPU_EVENTS (the latter requires some qemu patch that I will > post later). > > As we currently do not update event_exit_inst_len on #BP exits, > reinjecting fails unless event_exit_inst_len happens to be 1 from some > other exit. > Hmm, how does it work on SVM then where we do not have event_exit_inst_len so execution will resume on the same rip that caused #BP after event reinjection? -- Gleb. -- 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
