Re: [RFC PATCH v4 7/7] powerpc/powernv/pci-ioda: Add IOMMU_CAP_INTR_REMAP for IODA host bridge

[Yongji Xie]

On 2016/3/17 0:32, Alex Williamson wrote:
> On Mon,  7 Mar 2016 15:48:38 +0800
> Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx> wrote:
>
> > This patch adds IOMMU_CAP_INTR_REMAP for IODA host bridge so that
> > we can mmap MSI-X table in vfio driver.
> >
> > Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
> > ---
> >   arch/powerpc/platforms/powernv/pci-ioda.c |   17 +++++++++++++++++
> >   1 file changed, 17 insertions(+)
> >
> > diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> > index f90dc04..f01b9ab 100644
> > --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> > +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> > @@ -1955,6 +1955,20 @@ static struct iommu_table_ops pnv_ioda2_iommu_ops = {
> >   	.free = pnv_ioda2_table_free,
> >   };
> >   
> > +static bool pnv_ioda_iommu_capable(enum iommu_cap cap)
> > +{
> > +	switch (cap) {
> > +	case IOMMU_CAP_INTR_REMAP:
> > +		return true;
> > +	default:
> > +		return false;
> > +	}
> > +}
> > +
> > +static struct iommu_ops pnv_ioda_iommu_ops = {
> > +	.capable = pnv_ioda_iommu_capable,
> > +};
> > +
> >   static void pnv_pci_ioda_setup_dma_pe(struct pnv_phb *phb,
> >   				      struct pnv_ioda_pe *pe, unsigned int base,
> >   				      unsigned int segs)
> > @@ -3078,6 +3092,9 @@ static void pnv_pci_ioda_fixup(void)
> >   
> >   	/* Link NPU IODA tables to their PCI devices. */
> >   	pnv_npu_ioda_fixup();
> > +
> > +	/* Add IOMMU_CAP_INTR_REMAP */
> > +	bus_set_iommu(&pci_bus_type, &pnv_ioda_iommu_ops);
> >   }
> >   
> >   /*
>
> Doesn't this set you up for a world of hurt?  bus_set_iommu() calls
> iommu_bus_init() which sets up notifiers, which maybe you don't care
> about, but it also means that iommu_domain_alloc(&pci_bus_type) will
> segfault because you're not providing a domain_alloc callback here.

It seems to be hard to add IOMMU_CAP_INTR_REMAP on
PPC64 platform.

And can we add a new ioctl in vfio_iommu_driver to check
if interrupt remapping is supported so that we can use our
own way to determine that on PPC64 platform?

Thanks,
Yongji Xie