Re: [PATCH 8/8] x86-iommu: Fail early if vIOMMU specified after vfio-pci

[Peter Xu <peterx@redhat.com>]

On Thu, Oct 21, 2021 at 02:38:54PM +0200, Eric Auger wrote:
> Hi Peter,
> 
> On 10/21/21 12:42 PM, Peter Xu wrote:
> > Scan the pci bus to make sure there's no vfio-pci device attached before vIOMMU
> > is realized.
> >
> > Suggested-by: Igor Mammedov <imammedo@redhat.com>
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> >  hw/i386/x86-iommu.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> >
> > diff --git a/hw/i386/x86-iommu.c b/hw/i386/x86-iommu.c
> > index 86ad03972e..58abce7edc 100644
> > --- a/hw/i386/x86-iommu.c
> > +++ b/hw/i386/x86-iommu.c
> > @@ -21,6 +21,7 @@
> >  #include "hw/sysbus.h"
> >  #include "hw/i386/x86-iommu.h"
> >  #include "hw/qdev-properties.h"
> > +#include "hw/vfio/pci.h"
> >  #include "hw/i386/pc.h"
> >  #include "qapi/error.h"
> >  #include "qemu/error-report.h"
> > @@ -103,6 +104,16 @@ IommuType x86_iommu_get_type(void)
> >      return x86_iommu_default->type;
> >  }
> >  
> > +static void x86_iommu_pci_dev_hook(PCIBus *bus, PCIDevice *dev, void *opaque)
> > +{
> > +    Error **errp = (Error **)opaque;
> > +
> > +    if (object_dynamic_cast(OBJECT(dev), TYPE_VFIO_PCI)) {
> > +        error_setg(errp, "Device '%s' must be specified before vIOMMUs",
> > +                   TYPE_VFIO_PCI);
> if there are several VFIO-PCI devices set before the IOMMU, errp may be
> overriden
> as we do not exit the loop as soon as there is an error I think

Hmm, good point.  I won't worry too much about overriding yet as if there're
more devices violating the rule then reporting any of them should work - then
as the user tune the qemu cmdline it'll finally go right.

But I do see that error_setv() has an assertion on *errp being NULL.. I'll at
least make sure it won't trigger that assert by accident.

Thanks for spotting it!

-- 
Peter Xu