Gleb Natapov wrote: > On Tue, Feb 23, 2010 at 11:13:13AM +0100, Jan Kiszka wrote: >> Gleb Natapov wrote: >>> On Mon, Feb 22, 2010 at 06:51:22PM +0100, Jan Kiszka wrote: >>>> Call directly into the vendor services for getting/setting rflags in >>>> emulate_instruction to ensure injected TF survives the emulation. >>>> >>>> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> >>>> --- >>>> arch/x86/kvm/x86.c | 4 ++-- >>>> 1 files changed, 2 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >>>> index e2e03a4..19e8b28 100644 >>>> --- a/arch/x86/kvm/x86.c >>>> +++ b/arch/x86/kvm/x86.c >>>> @@ -3468,7 +3468,7 @@ int emulate_instruction(struct kvm_vcpu *vcpu, >>>> kvm_x86_ops->get_cs_db_l_bits(vcpu, &cs_db, &cs_l); >>>> >>>> vcpu->arch.emulate_ctxt.vcpu = vcpu; >>>> - vcpu->arch.emulate_ctxt.eflags = kvm_get_rflags(vcpu); >>>> + vcpu->arch.emulate_ctxt.eflags = kvm_x86_ops->get_rflags(vcpu); >>> So now emulator runs with injected TF? Hmm, then may be emulator should >>> inject DB when appropriate and caller of emulate_instruction() should >>> emulate DB intercept if external debugging is going on? >> That is what patch 6 aims at, both for external as well as >> guest-internal debugging. >> > It does at the wrong level. It tries to do it above emulator, but only emulator > knows what is the sate of instruction emulation and when emulation is completed. > If at this point TF is set it inject DB trap. The code above checks if > DB intercept is enabled when DB is injected and calls usual DB intercept > path. Sorry, can't follow, your description does not match the above code for me. This patch just ensures that we do not loose TF across emulation and, by itself, already improves guest debugging: it allows to step over emulated blocks with one instruction offset. And it has no side effects as the emulator does not evaluate TF yet (before patch 6). Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- 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
