Re: [PATCH 2/3] intel-iommu: fail DEVIOTLB_UNMAP without dt mode

[Jason Wang]

On Fri, Dec 2, 2022 at 12:03 AM Peter Xu <peterx@redhat.com> wrote:
>
> On Tue, Nov 29, 2022 at 04:10:36PM +0800, Jason Wang wrote:
> > Without dt mode, device IOTLB notifier won't work since guest won't
> > send device IOTLB invalidation descriptor in this case. Let's fail
> > early instead of misbehaving silently.
> >
> > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > ---
> >  hw/i386/intel_iommu.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > index 9143376677..d025ef2873 100644
> > --- a/hw/i386/intel_iommu.c
> > +++ b/hw/i386/intel_iommu.c
> > @@ -3179,6 +3179,7 @@ static int 
> > vtd_iommu_notify_flag_changed(IOMMUMemoryRegion *iommu,
> >  {
> >      VTDAddressSpace *vtd_as = container_of(iommu, VTDAddressSpace, iommu);
> >      IntelIOMMUState *s = vtd_as->iommu_state;
> > +    X86IOMMUState *x86_iommu = X86_IOMMU_DEVICE(s);
> >
> >      /* TODO: add support for VFIO and vhost users */
> >      if (s->snoop_control) {
> > @@ -3193,6 +3194,13 @@ static int 
> > vtd_iommu_notify_flag_changed(IOMMUMemoryRegion *iommu,
> >                           PCI_FUNC(vtd_as->devfn));
> >          return -ENOTSUP;
> >      }
> > +    if (!x86_iommu->dt_supported && (new & IOMMU_NOTIFIER_DEVIOTLB_UNMAP)) 
> > {
> > +        error_setg_errno(errp, ENOTSUP,
> > +                         "device %02x.%02x.%x requires device IOTLB mode",
> > +                         pci_bus_num(vtd_as->bus), PCI_SLOT(vtd_as->devfn),
> > +                         PCI_FUNC(vtd_as->devfn));
> > +        return -ENOTSUP;
> > +    }
>
> While my r-b holds.. let's also do this for amd-iommu in the same patch?
> dt never supported there, so we can fail as long as DEVIOTLB registered.

Looks like there's one implementation:

Per spec:

""
The INVALIDATE_IOTLB_PAGES command is only present in IOMMU
implementations that support remote IOTLB caching of translations (see
Capability Offset 00h[IotlbSup]). This command instructs the specified
device to invalidate the given range of addresses in its IOTLB. The
size of the invalidate command is determined by the S bit and the
address.
""

And it has one implementation (though buggy) iommu_inval_iotlb() which
doesn't trigger any DEVIOTLB_UNMAP notifier.

We can leave this for the future.

(Last time I tried amd-iommu it didn't even boot).

Thanks

>
> >
> >      /* Update per-address-space notifier flags */
> >      vtd_as->notifier_flags = new;
> > --
> > 2.25.1
> >
>
> --
> Peter Xu
>