Gleb Natapov wrote:
> On Tue, May 05, 2009 at 10:45:20AM +0200, Jan Kiszka wrote:
>>> @@ -2331,8 +2358,16 @@ static void enable_nmi_window(struct kvm_vcpu *vcpu)
>>> {
>>> struct vcpu_svm *svm = to_svm(vcpu);
>>>
>>> - if (svm->vmcb->control.int_state & SVM_INTERRUPT_SHADOW_MASK)
>>> - enable_irq_window(vcpu);
>>> + if ((svm->vcpu.arch.hflags & (HF_NMI_MASK | HF_IRET_MASK))
>>> + == HF_NMI_MASK)
>>> + return; /* IRET will cause a vm exit */
>>> +
>>> + /* Something prevents NMI from been injected. Single step over
>>> + possible problem (IRET or exception injection or interrupt
>>> + shadow) */
>>> + vcpu->arch.singlestep = true;
>>> + svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
>> Can you single-step like this out of an IRQ handler? I mean, IRET will
>> restore the flags from the stack, and those settings should be
>> overwritten. Or am I missing something?
>>
> It seems to be working :) Shouldn't CPU checks single step before
> executing IRET and thus using old flags value? It is interesting to
> check what rflag value is immediately after IRET.
Hmm, guess I have to re-read some manuals. But regarding
rflags-after-iret, I think it should be cleared due to that restoring
from the stack.
Jan
--
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux
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