Re: [patch V2 04/25] x86/apic: Make apic_pending_intr_clear() more robust

From: Thomas Gleixner
Date: Sun Jul 07 2019 - 04:37:34 EST

On Fri, 5 Jul 2019, Paolo Bonzini wrote:
> On 05/07/19 22:25, Thomas Gleixner wrote:
> > The more interesting question is whether this is all relevant. If I
> > understood the issue correctly then this is mitigated by proper interrupt
> > remapping.
> Yes, and for Linux we're good I think. VFIO by default refuses to use
> the IOMMU if interrupt remapping is absent or disabled, and KVM's own

Confused. If it does not use IOMMU, what does it do? Hand in the device as
is and let the guest fiddle with it unconstrained or does it actually
refuse to pass through?

> (pre-VFIO) IOMMU support was removed a couple years ago. I guess the
> secure boot lockdown patches should outlaw VFIO's
> allow_unsafe_interrupts option, but that's it.

I'm not worried too much about command line options. The important thing is
the default behaviour. If an admin decides to do something stupid, so be