Re: [RFC 03/12] KVM/VMX: Use the new host mapping API for virtual_apic_page

[KarimAllah Ahmed]

On 02/05/2018 11:26 PM, Jim Mattson wrote:
> On Mon, Feb 5, 2018 at 10:48 AM KarimAllah Ahmed <karahmed@xxxxxxxxx> wrote:
>
> > @@ -5264,9 +5264,8 @@ static void
> vmx_complete_nested_posted_interrupt(struct kvm_vcpu *vcpu)
>
> >           max_irr = find_last_bit((unsigned long
> *)vmx->nested.pi_desc->pir, 256);
> >           if (max_irr != 256) {
> > -               vapic_page = kmap(vmx->nested.virtual_apic_page);
> > +               vapic_page = vmx->nested.virtual_apic_mapping.kaddr;
> >                   __kvm_apic_update_irr(vmx->nested.pi_desc->pir,
> vapic_page);
> > -               kunmap(vmx->nested.virtual_apic_page);
>
> Your kernel mapping now survives exits to userspace. I didn't think that
> was kosher, but I'd be happy to hear that I'm wrong.

Can you elaborate a bit? I do not really understand what is the concern.

> > @@ -7502,10 +7501,8 @@ static void free_nested(struct vcpu_vmx *vmx)
> >           /* Unpin physical memory we referred to in the vmcs02 */
> >           if (vmx->nested.apic_access_mapping.pfn)
>
> kvm_release_host_mapping(&vmx->nested.apic_access_mapping, true);
> > -       if (vmx->nested.virtual_apic_page) {
> > -               kvm_release_page_dirty(vmx->nested.virtual_apic_page);
> > -               vmx->nested.virtual_apic_page = NULL;
> > -       }
> > +       if (vmx->nested.virtual_apic_mapping.pfn)
> > +
> kvm_release_host_mapping(&vmx->nested.virtual_apic_mapping, true);
>
> Is the host PFN guaranteed to be non-zero?

Yeah, I should not have assumed that PFN zero is invalid. Will fix.
Amazon Development Center Germany GmbH
Berlin - Dresden - Aachen
main office: Krausenstr. 38, 10117 Berlin
Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger
Ust-ID: DE289237879
Eingetragen am Amtsgericht Charlottenburg HRB 149173 B