Re: [Xen-devel] [PATCH v6] x86/hvm/viridian: Enable APIC assist enlightenment

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 24 March 2016 13:51
> To: Paul Durrant
> Cc: Andrew Cooper; Wei Liu; Ian Jackson; Stefano Stabellini; xen-
> devel@xxxxxxxxxxxxxxxxxxxx; Keir (Xen.org)
> Subject: Re: [PATCH v6] x86/hvm/viridian: Enable APIC assist enlightenment
> 
> >>> On 18.03.16 at 11:32, <paul.durrant@xxxxxxxxxx> wrote:
> > @@ -278,6 +281,53 @@ static void teardown_apic_assist(struct vcpu *v)
> >      put_page_and_type(page);
> >  }
> >
> > +void viridian_start_apic_assist(struct vcpu *v, int vector)
> > +{
> > +    uint32_t *va = v->arch.hvm_vcpu.viridian.apic_assist.va;
> > +
> > +    if ( !va )
> > +        return;
> > +
> > +    /*
> > +     * If there is already an assist pending then something has gone
> > +     * wrong and the VM will most likely hang so force a crash now
> > +     * to make the problem clear.
> > +     */
> > +    if ( v->arch.hvm_vcpu.viridian.apic_assist.vector >= 0 )
> > +        domain_crash(v->domain);
> > +
> > +    v->arch.hvm_vcpu.viridian.apic_assist.vector = vector;
> 
> Considering the osstest failures I (see also IRC) I now wonder
> what happens if the guest gets migrated while a vCPU has this
> field holding a valid vector, namely how ...
> 
> > @@ -1170,10 +1183,27 @@ int vlapic_has_pending_irq(struct vcpu *v)
> >           !nestedhvm_vcpu_in_guestmode(v) )
> >          return irr;
> >
> > +    /*
> > +     * If APIC assist was used then there may have been no EOI so
> > +     * we need to clear the requisite bit from the ISR here, before
> > +     * comparing with the IRR.
> > +     */
> > +    vector = viridian_complete_apic_assist(v);
> > +    if ( vector != -1 )
> > +        vlapic_clear_vector(vector, &vlapic->regs->data[APIC_ISR]);
> 
> ... this would then be taken care of on the new host.
>

Yes, you're right. I need to add that field to the viridian vcpu state. Patch 
coming a.s.a.p.

  Paul


 
> Jan


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