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

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

> -----Original Message-----
> From: Andrew Cooper [mailto:andrew.cooper3@citrix.com]
> Sent: Friday, March 27, 2015 6:06 PM
> To: Wu, Feng; xen-devel@lists.xen.org
> Cc: Zhang, Yang Z; Tian, Kevin; keir@xen.org; JBeulich@suse.com
> Subject: Re: [Xen-devel] [RFC v1 02/15] vt-d: VT-d Posted-Interrupts feature
> detection
> 
> 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.

Broadwell EP should have this feature, but the hardware with this feature
should be available later this year.

Thanks,
Feng
> 
> ~Andrew