Re: [Qemu-devel] [PATCH 1/1 V5] kernel/kvm: introduce KVM_SET_LINT1 and fix improper nmi emulation

[Avi Kivity]

On 10/17/2011 11:17 AM, Lai Jiangshan wrote:
> On 10/16/2011 05:39 PM, Avi Kivity wrote:
> > On 10/14/2011 11:03 AM, Lai Jiangshan wrote:
> >> Currently, NMI interrupt is blindly sent to all the vCPUs when NMI
> >> button event happens. This doesn't properly emulate real hardware on
> >> which NMI button event triggers LINT1. Because of this, NMI is sent to
> >> the processor even when LINT1 is masked in LVT. For example, this
> >> causes the problem that kdump initiated by NMI sometimes doesn't work
> >> on KVM, because kdump assumes NMI is masked on CPUs other than CPU0.
> >>
> >> With this patch, we introduce introduce KVM_SET_LINT1,
> >> and we can use KVM_SET_LINT1 to correctly emulate NMI button
> >> without change the old KVM_NMI behavior.
> >>  
> >> @@ -759,6 +762,8 @@ struct kvm_clock_data {
> >>  #define KVM_CREATE_SPAPR_TCE        _IOW(KVMIO,  0xa8, struct 
> >> kvm_create_spapr_tce)
> >>  /* Available with KVM_CAP_RMA */
> >>  #define KVM_ALLOCATE_RMA    _IOR(KVMIO,  0xa9, struct kvm_allocate_rma)
> >> +/* Available with KVM_CAP_SET_LINT1 for x86 */
> >> +#define KVM_SET_LINT1               _IO(KVMIO,   0xaa)
> >>  
> >>
> > 
> > LINT1 may have been programmed as a level -triggered interrupt instead
> > of edge triggered (NMI or interrupt).  We can use the ioctl argument for
> > the level (and pressing the NMI button needs to pulse the level to 1 and
> > back to 0).
> > 
>
> Hi, Avi,
>
> How to handle level=0 in the kernel?
> Or just ignore it?

It needs to be handled according to the delivery mode, polarity, and
trigger mode bits in the LVT.

For example, a Fixed delivery mode with polarity 1 and level trigger
mode will post the interrupt as long as it is in level 0 and not masked
by the ISR.  __apic_accept_irq() should handle this.

-- 
error compiling committee.c: too many arguments to function