Re: [PATCH] KVM: X86: Fix async pf caused null-ptr-deref

[Wanpeng Li]

On Mon, 29 Jun 2020 at 23:42, Sean Christopherson
<sean.j.christopherson@xxxxxxxxx> wrote:
>
> On Mon, Jun 29, 2020 at 03:59:25PM +0200, Paolo Bonzini wrote:
> > On 29/06/20 15:46, Vitaly Kuznetsov wrote:
> > >> +  if (!lapic_in_kernel(vcpu))
> > >> +          return 1;
> > >> +
> > > I'm not sure how much we care about !lapic_in_kernel() case but this
> > > change should be accompanied with userspace changes to not expose
> > > KVM_FEATURE_ASYNC_PF_INT or how would the guest know that writing a
> > > legitimate value will result in #GP?
> >
> > Almost any pv feature is broken with QEMU if kernel_irqchip=off.  I
> > wouldn't bother and I am seriously thinking of dropping all support for
> > that, including:
>
> Heh, based on my limited testing, that could be "Almost everything is
> broken with Qemu if kernel_irqchip=off".

It is broken for several years. :)