Re: [Xen-devel] [RFC v1 02/15] vt-d: VT-d Posted-Interrupts feature detection

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 27/03/15 01:21, Wu, Feng wrote:
> > > +     * Remapping, and Posted Interrupt
> > >         */
> > >        for_each_drhd_unit ( drhd )
> > >        {
> > > @@ -2146,7 +2148,13 @@ int __init intel_vtd_setup(void)
> > >                iommu_qinval = 0;
> > >
> > >            if ( iommu_intremap && !ecap_intr_remap(iommu->ecap) )
> > > +        {
> > >                iommu_intremap = 0;
> > > +            iommu_intpost = 0;
> > > +        }
> > > +
> > > +        if ( iommu_intpost && !cap_intr_post(iommu->cap))
> > Missing space inside the outer bracket.
> >
> > I am wondering whether it might be easier, instead of having
> > "iommu_intremap = 0; iommu_intpost = 0" all over the place, to instead
> > insist that one must check "iommu_intremap && iommu_intpost".
> It that case, user must check "iommu_intremap && iommu_intpost" together,
> my idea in this patchset is the when iommu_intpost == 1 guarantees "iommu_intremap 
> == 1",
> so we only need to check iommu_intpost later.
If the configuration gets much more complicated, it might be worth 
introducing iommu_disable(foo)/iommu_enable(foo) functions which take 
care of ensuring that the interdependences are met.
For now, this is probably the more simple solution.

> > Out of interest, which platforms have intpost capabilities?
> Another Broadwell platform, not launched yet.
Broadwell EP/EX ?  I have an SDP to hand, but as it claims to be a 
"Genuine Intel(R) CPU 0000 @ 1.70GHz", it is not completely trivial to 
work out what platform it is exactly.
~Andrew

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