Hi Gleb,
My code works by setting "vcpu->arch.nmi_pending = 1;" inside
vcpu_enter_guest().
Thanks,
Jiaqing
2009/7/27 Gleb Natapov <gleb@xxxxxxxxxx>:
> On Sun, Jul 26, 2009 at 09:25:34PM +0200, Jiaqing Du wrote:
>> Hi Gleb,
>>
>> Thanks for your reply.
>>
>> 2009/7/26 Gleb Natapov <gleb@xxxxxxxxxx>:
>> > On Sat, Jul 25, 2009 at 10:46:39PM +0200, Jiaqing Du wrote:
>> >> Hi list,
>> >>
>> >> I'm trying to extend OProfile to support guest profiling. One step of
>> >> my work is to push an NMI to the guest(s) when a performance counter
>> >> overflows. Please correct me if the following is not correct:
>> >>
>> >> counter overflow --> NMI to host --> VM exit --> "int $2" to handle
>> >> NMI on host --> ... --> VM entry --> NMI to guest
>> >>
>> > Correct except the last step (--> NMI to guest). Host nmi is not
>> > propagated to guests.
>>
>> Yes. I need to add some code to propagate host NMI to guests.
>> >
>> >> On the path between VM-exit and VM-entry, I want to push an NMI to the
>> >> guest. I tried to put the following code on the path, but never
>> >> succeeded. Various wired things happened, such as KVM hangs, guest
>> >> kernel oops, and host hangs. I tried both code with Linux 2.6.30 and
>> >> version 88.
>> >>
>> >> if (vmx_nmi_allowed()) { vmx_inject_nmi(); }
>> >>
>> >> Any suggestions? Where is the right place to push an NMI and what are
>> >> the necessary checks?
>> > Call kvm_inject_nmi(vcpu). And don't forget to vcpu_load(vcpu) before
>> > doing it. See kvm_vcpu_ioctl_nmi().
>>
>> Based on the code with Linux 2.6.30, what kvm_inject_nmi(vcpu) does is
>> just set vcpu->arch.nmi_pending to 1. kvm_vcpu_ioctl_nmi() puts
>> vcpu_load() before the setting and vcpu_put() after it.
>>
>> I need to push host NMI to guests between a VM-exit and a VM-entry
>> after that. The VM-exit is due to an NMI caused by performance counter
>> overflow. The following code with vcpu_enter_guest(), which is
>> surrounded by a vcpu_load() and vcpu_put(), checks this
>> vcpu->arch.nmi_pending and other related flags to decide whether an
>> NMI should be pushed to guests.
>>
>> if (vcpu->arch.exception.pending)
>> __queue_exception(vcpu);
>> else if (irqchip_in_kernel(vcpu->kvm))
>> kvm_x86_ops->inject_pending_irq(vcpu);
>> else
>> kvm_x86_ops->inject_pending_vectors(vcpu, kvm_run);
>>
>> What I did is given below:
>>
>> 3097 static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> 3098 {
>> ... ...
>>
>> 3156 if (kvm_vm_exit_on_cnt_overflow) {
>> 3157 vcpu->arch.nmi_pending = 1;
>> 3158 }
>> 3159
>> 3160 if (vcpu->arch.exception.pending)
>> 3161 __queue_exception(vcpu);
>> 3162 else if (irqchip_in_kernel(vcpu->kvm))
>> 3163 kvm_x86_ops->inject_pending_irq(vcpu);
>> 3164 else
>> 3165 kvm_x86_ops->inject_pending_vectors(vcpu, kvm_run);
>>
>> ... ....
>> 3236 }
>>
>> In vcpu_enter_guest(), before this part of code is reached,
>> vcpu->arch.nmi_pending is set to 1 if the VM-exit is due to
>> performance counter overflow. Still, no NMIs are seen by the guests. I
>> also tried to put this "vcpu->arch.nmi_pending = 1;" somewhere else on
>> the path between a VM-exit and VM-entry, it does not seem to work
>> neither. Only vmx_inject_nmi() manages to push NMIs to guests, but
>> without right sanity checks, it causes various wired host and guest
>> behaviors.
>>
>> To inject NMIs on the path between a VM-exit and VM-entry, what's to try next?
>>
> If you set vcpu->arch.nmi_pending here there vmx_inject_nmi() will be
> called inside kvm_x86_ops->inject_pending_irq(vcpu) (if there is not
> pending exceptions or interrupt at that moment), so if NMI is not
> injected either you have a bug somewhere (why kvm_vm_exit_on_cnt_overflow
> is global?) or you guest ignores NMIs. Does your guest react to NMI if
> you send it via qemu monitor (type "nmi 0" in qemu monitor).
>
> Post you code here, may be I'll see something.
>
> --
> Gleb.
>
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