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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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).

Jan


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