Re: [RFC][PATCH 3/4] KVM: VMX: Enable NMI with in-kernel irqchip

["Yang, Sheng" <sheng.yang@intel.com>]

On Tuesday 13 May 2008 14:42:17 Yang, Sheng wrote:
> On Monday 12 May 2008 15:54:00 Avi Kivity wrote:
> > Yang, Sheng wrote:
> > > On Friday 09 May 2008 23:49:13 Avi Kivity wrote:
> > >> Yang, Sheng wrote:
> > >>> From 4942a5c35c97e5edb6fe1303e04fb86f25cac345 Mon Sep 17 00:00:00
> > >>> 2001 From: Sheng Yang <sheng.yang@intel.com>
> > >>> Date: Thu, 8 May 2008 16:00:57 +0800
> > >>> Subject: [PATCH 3/4] KVM: VMX: Enable NMI with in-kernel irqchip
> > >>>
> > >>>
> > >>>  static void kvm_do_inject_irq(struct kvm_vcpu *vcpu)
> > >>>  {
> > >>>  	int word_index = __ffs(vcpu->arch.irq_summary);
> > >>> @@ -2146,9 +2159,11 @@ static void do_interrupt_requests(struct
> > >>> kvm_vcpu *vcpu,
> > >>>  		/*
> > >>>  		 * Interrupts blocked.  Wait for unblock.
> > >>>  		 */
> > >>> -		cpu_based_vm_exec_control |= CPU_BASED_VIRTUAL_INTR_PENDING;
> > >>> +		cpu_based_vm_exec_control |=
> > >>> +			CPU_BASED_VIRTUAL_INTR_PENDING;
> > >>>  	else
> > >>> -		cpu_based_vm_exec_control &= ~CPU_BASED_VIRTUAL_INTR_PENDING;
> > >>> +		cpu_based_vm_exec_control &=
> > >>> +			~CPU_BASED_VIRTUAL_INTR_PENDING;
> > >>
> > >> This seems spurious.
> > >
> > > Sorry, seems I am too anxious to keep it in hand... I would like to
> > > check it much careful in the future.
> > >
> > >>>  	/* We need to handle NMIs before interrupts are enabled */
> > >>> -	if ((intr_info & INTR_INFO_INTR_TYPE_MASK) == 0x200) { /* nmi */
> > >>> +	if ((intr_info & INTR_INFO_INTR_TYPE_MASK) == 0x200) {
> > >>>  		KVMTRACE_0D(NMI, vcpu, handler);
> > >>> -		asm("int $2");
> > >>> +		if (!cpu_has_virtual_nmis())
> > >>> +			asm("int $2");
> > >>>  	}
> > >>>  }
> > >>
> > >> That's a host nmi.  So does the PIN_BASED_VIRTUAL_NMI mean NMIs are
> > >> handled like unacked host interrupts?
> > >
> > > Not exactly. No host NMI here if Virtual_NMI is set. Copy from SDM 3B
> > > table 20-5:
> > >
> > > "If this control(Virtual NMIs) is 1, NMIs are never blocked and the
> > > “blocking by NMI” bit (bit 3) in the interruptibility-state field
> > > indicates “virtual-NMI blocking” (see Table 20-3). This control also
> > > interacts with the “NMI-window exiting” VM-execution control (see
> > > Section 20.6.2)."
> >
> > I still don't understand.  What does "NMIs are never blocked" mean?
> > what happens if an NMI occurs while in guest mode?  Obviously we don't
> > want it to be delivered to the guest.
>
> Oops, I neglected it... When virtual_nmi is set, the host NMI would routed
> to handle_exception. And we would handle it there, by judged the vector
> number.
>
> I will posted the updated patchset soon.

Faint, misunderstood again... Seems the cold affact my thinking... 

Anyway, I will updated my patchset. Thanks!

-- 
Thanks
Yang, Sheng

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