Gleb Natapov wrote:
> On Tue, Feb 16, 2010 at 12:08:58PM +0200, Gleb Natapov wrote:
>>>>> Besides this, proper #DB forwarding to the guest was missing.
>>>> During NMI injection? How to reproduce?
>>> Inject, e.g., an NMI over code with TF set. A bit harder is placing a
>>> guest HW breakpoint at the spot the NMI handler returns to.
>>>
>> Will try to reproduce.
>>
> How can I make gdb to run debugged process with TF set? Is this patch
> fixes it:
>
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 52f78dd..b85b200 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -109,6 +109,7 @@ struct vcpu_svm {
> struct nested_state nested;
>
> bool nmi_singlestep;
> + bool nmi_singlestep_tf;
> };
>
> /* enable NPT for AMD64 and X86 with PAE */
> @@ -1221,9 +1222,14 @@ static int db_interception(struct vcpu_svm *svm)
>
> if (svm->nmi_singlestep) {
> svm->nmi_singlestep = false;
> - if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP))
> + if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP)) {
> svm->vmcb->save.rflags &=
> ~(X86_EFLAGS_TF | X86_EFLAGS_RF);
> + if (svm->nmi_singlestep_tf) {
> + svm->vmcb->save.rflags |= X86_EFLAGS_TF;
> + kvm_queue_exception(&svm->vcpu, DB_VECTOR);
> + }
> + }
> update_db_intercept(&svm->vcpu);
> }
>
> @@ -2586,6 +2592,7 @@ static void enable_nmi_window(struct kvm_vcpu *vcpu)
> possible problem (IRET or exception injection or interrupt
> shadow) */
> svm->nmi_singlestep = true;
> + svm->nmi_singlestep_tf = (svm->vmcb->save.rflags | X86_EFLAGS_TF);
> svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
> update_db_intercept(vcpu);
> }
That's closer. However, I've a version here that restores TF&RF only if
you did not execute an IRET but stepped over the shadow (which is still
not correct either, e.g. when stepping popf). I will break up my patch
into parts that fix the issues separately so that we can decide what to
merge.
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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