Re: [Qemu-devel] [PATCH] intel_iommu: make sure its init before PCI dev

[Marcel Apfelbaum]

On 02/23/2017 10:16 AM, Peter Xu wrote:
> On Thu, Feb 23, 2017 at 10:10:57AM +0200, Marcel Apfelbaum wrote:
> > On 02/23/2017 05:06 AM, Peter Xu wrote:
> > > On Wed, Feb 22, 2017 at 10:30:47AM -0700, Alex Williamson wrote:
> > > > On Wed, 22 Feb 2017 13:49:25 +0800
> > > > Peter Xu <address@hidden> wrote:
> > > >
> > > > > Intel vIOMMU devices are created with "-device" parameter, while here
> > > > > actually we need to make sure this device will be created before some
> > > > > other PCI devices (like vfio-pci devices) so that we know iommu_fn will
> > > > > be setup correctly before realizations of those PCI devices.
> > > > >
> > > > > Here we do explicit check to make sure intel-iommu device will be inited
> > > > > before all the rest of the PCI devices. This is done by checking against
> > > > > the devices dangled under current root PCIe bus and we should see
> > > > > nothing there besides integrated ICH9 ones.
> >
> > Hi,
> >
> > Commit b86eacb8 (hw/pci: delay bus_master_enable_region initialization)
> > creates the IOMMU memory region at machine_done time so the
> > devices creation order wouldn't matter.
> >
> > I don't think we use the iommu_fn before machine_done.
> > What have I missed?
>
> Hi, Marcel,
>
> The problem is that vfio-pci will need to fetch the pci address space
> during realization (pci_device_iommu_address_space() is called in
> vfio_realize()).
>
> Any thoughts? Thanks,

Sure, I'll try to find a solution, but first I need to
understand why vfio-pci need to access the pci_device_iommu_address_space
so early. Maybe we can delay this also to machine_done stage.

Thanks,
Marcel

> -- peterx