Re: [Xen-devel] [PATCH v3 1/6] VMX: Statically assign two PI hooks

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Thursday, September 1, 2016 5:23 PM
> To: Wu, Feng <feng.wu@xxxxxxxxx>
> Cc: andrew.cooper3@xxxxxxxxxx; dario.faggioli@xxxxxxxxxx;
> george.dunlap@xxxxxxxxxxxxx; Tian, Kevin <kevin.tian@xxxxxxxxx>; xen-
> devel@xxxxxxxxxxxxx
> Subject: RE: [PATCH v3 1/6] VMX: Statically assign two PI hooks
> 
> >>> On 01.09.16 at 11:13, <feng.wu@xxxxxxxxx> wrote:
> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> Sent: Thursday, September 1, 2016 4:17 PM
> >> >>> On 31.08.16 at 05:56, <feng.wu@xxxxxxxxx> wrote:
> >> > --- a/xen/arch/x86/hvm/vmx/vmx.c
> >> > +++ b/xen/arch/x86/hvm/vmx/vmx.c
> >> > @@ -207,8 +207,6 @@ void vmx_pi_hooks_assign(struct domain *d)
> >> >      ASSERT(!d->arch.hvm_domain.vmx.vcpu_block);
> >> >
> >> >      d->arch.hvm_domain.vmx.vcpu_block = vmx_vcpu_block;
> >> > -    d->arch.hvm_domain.vmx.pi_switch_from = vmx_pi_switch_from;
> >> > -    d->arch.hvm_domain.vmx.pi_switch_to = vmx_pi_switch_to;
> >> >      d->arch.hvm_domain.vmx.pi_do_resume = vmx_pi_do_resume;
> >> >  }
> >>
> >> I'm sure I've said so before: While I can see why you want the
> >> adjustment to vmx_pi_hooks_deassign(), I don't see why leaving
> >> out this and ...
> >
> > As mentioned in the comments of this patch, these two hooks are also
> > needed for CPU side PI, so we cannot install here and ...
> 
> I've just read it again, and to me it doesn't say so. I.e. ...
> 
> >> > @@ -236,6 +232,12 @@ static int vmx_domain_initialise(struct domain *d)
> >> >      if ( (rc = vmx_alloc_vlapic_mapping(d)) != 0 )
> >> >          return rc;
> >> >
> >> > +    if ( iommu_intpost )
> >> > +    {
> >> > +        d->arch.hvm_domain.vmx.pi_switch_from = vmx_pi_switch_from;
> >> > +        d->arch.hvm_domain.vmx.pi_switch_to = vmx_pi_switch_to;
> >> > +    }
> >> > +
> >> >      return 0;
> >> >  }
> >>
> >> ... this would conflict with the goal of the patch.
> >
> > ... Yes this is incorrect, I should install these two hooks when CPU side 
> > PI is
> > supported.
> 
> ... you'd then additionally need to explain what bug there is without
> these hooks and with only CPU side PI present (iirc that's functionality
> which has been there before the VT-d part).

Oh, my bad, I mixed things up. Then I should install these two hooks when
the first device assignment happens and don't zap it after that. Thanks for
the comments!

Thanks,
Feng

> 
> Jan


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