RE: [PATCH v2 01/11] x86/hvm: drop vcpu parameter from vlapic EOI callbacks

["Durrant, Paul" <pdurrant@xxxxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: 02 October 2020 09:48
> To: Roger Pau Monne <roger.pau@xxxxxxxxxx>; Wei Liu <wl@xxxxxxx>; Paul 
> Durrant <paul@xxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Andrew Cooper 
> <andrew.cooper3@xxxxxxxxxx>; Durrant, Paul
> <pdurrant@xxxxxxxxxxxx>
> Subject: RE: [EXTERNAL] [PATCH v2 01/11] x86/hvm: drop vcpu parameter from 
> vlapic EOI callbacks
> 
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> 
> On 30.09.2020 12:40, Roger Pau Monne wrote:
> > --- a/xen/arch/x86/hvm/vlapic.c
> > +++ b/xen/arch/x86/hvm/vlapic.c
> > @@ -459,13 +459,10 @@ void vlapic_EOI_set(struct vlapic *vlapic)
> >
> >  void vlapic_handle_EOI(struct vlapic *vlapic, u8 vector)
> >  {
> > -    struct vcpu *v = vlapic_vcpu(vlapic);
> > -    struct domain *d = v->domain;
> > -
> >      if ( vlapic_test_vector(vector, &vlapic->regs->data[APIC_TMR]) )
> > -        vioapic_update_EOI(d, vector);
> > +        vioapic_update_EOI(vector);
> >
> > -    hvm_dpci_msi_eoi(d, vector);
> > +    hvm_dpci_msi_eoi(vector);
> >  }
> 
> What about viridian_synic_wrmsr() -> vlapic_EOI_set() ->
> vlapic_handle_EOI()? You'd probably have noticed this if you
> had tried to (consistently) drop the respective parameters from
> the intermediate functions as well.
> 
> Question of course is in how far viridian_synic_wrmsr() for
> HV_X64_MSR_EOI makes much sense when v != current. Paul, Wei?
> 

I don't think it makes any sense. I think it would be fine to only do it if v 
== current.

  Paul

> A secondary question of course is whether passing around the
> pointers isn't really cheaper than the obtaining of 'current'.
> 
> Jan