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

Yang, Sheng
2008-05-12T05:19:19Z

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)."