Re: [Qemu-devel] [PATCH 13/13] qdev-properties: Add pci-devaddr property

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Jun 10, 2012 at 12:52:45PM +0200, Jan Kiszka wrote:
> On 2012-06-10 12:49, Michael S. Tsirkin wrote:
> > On Sun, Jun 10, 2012 at 12:14:36PM +0200, Jan Kiszka wrote:
> >> On 2012-06-10 11:35, Michael S. Tsirkin wrote:
> >>> On Mon, Jun 04, 2012 at 10:52:21AM +0200, Jan Kiszka wrote:
> >>>> Add a property to receive a fully qualified PCI device address.
> >>>>
> >>>> Will be used by KVM device assignment.
> >>>>
> >>>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> >>>
> >>> I'd like to ponder this a bit more.  What bothers me is that this mixes
> >>> two things:
> >>> 	- addressing of qemu devices
> >>> 		Using full device addresses there is a legacy feature,
> >>> 		users really should supply the parent bus and
> >>> 		the bus local address.
> >>> 	- addressing devices on the linux host for assignment
> >>> 		It so happens that the syntax matches
> >>> 		the legacy naming very closely,
> >>> 		but conceptually is completely unrelated
> >>
> >> We can keep code duplications, of course.
> >>
> >>>
> >>>> ---
> >>>>  hw/qdev-properties.c |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
> >>>>  hw/qdev.h            |    3 +++
> >>>>  2 files changed, 51 insertions(+), 0 deletions(-)
> >>>>
> >>>> diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c
> >>>> index 32e41f1..6634f22 100644
> >>>> --- a/hw/qdev-properties.c
> >>>> +++ b/hw/qdev-properties.c
> >>>> @@ -946,6 +946,54 @@ PropertyInfo qdev_prop_pci_devfn = {
> >>>>      .max   = 0xFFFFFFFFULL,
> >>>>  };
> >>>>  
> >>>> +static void get_pci_devaddr(Object *obj, Visitor *v, void *opaque,
> >>>> +                            const char *name, Error **errp)
> >>>> +{
> >>>> +    DeviceState *dev = DEVICE(obj);
> >>>> +    Property *prop = opaque;
> >>>> +    PCIDeviceAddress *addr = qdev_get_prop_ptr(dev, prop);
> >>>> +    char buffer[10 + 3 + 1];
> >>>> +    char *p = buffer;
> >>>> +
> >>>> +    snprintf(buffer, sizeof(buffer), "%04x:%02x:%02x.%02x",
> >>>> +             addr->domain, addr->bus, addr->slot, addr->function);
> >>>> +
> >>>> +    visit_type_str(v, &p, name, errp);
> >>>> +}
> >>>> +
> >>>> +static void set_pci_devaddr(Object *obj, Visitor *v, void *opaque,
> >>>> +                            const char *name, Error **errp)
> >>>> +{
> >>>> +    DeviceState *dev = DEVICE(obj);
> >>>> +    Property *prop = opaque;
> >>>> +    PCIDeviceAddress *addr = qdev_get_prop_ptr(dev, prop);
> >>>> +    Error *local_err = NULL;
> >>>> +    char *str;
> >>>> +
> >>>> +    if (dev->state != DEV_STATE_CREATED) {
> >>>> +        error_set(errp, QERR_PERMISSION_DENIED);
> >>>> +        return;
> >>>> +    }
> >>>> +
> >>>> +    visit_type_str(v, &str, name, &local_err);
> >>>> +    if (local_err) {
> >>>> +        error_propagate(errp, local_err);
> >>>> +        return;
> >>>> +    }
> >>>> +
> >>>> +    if (qemu_parse_pci_devaddr(str, addr,
> >>>> +                               PCI_DEVADDR_WITH_DOM_BUS_OPT |
> >>>> +                               PCI_DEVADDR_WITH_FUNC) < 0) {
> >>>> +        error_set_from_qdev_prop_error(errp, EINVAL, dev, prop, str);
> >>>> +    }
> >>>> +}
> >>>> +
> >>>> +PropertyInfo qdev_prop_pci_devaddr = {
> >>>> +    .name  = "pci-devaddr",
> >>>
> >>> This is a very confusing name.  Something like host-pci-address?
> >>
> >> That might be an option.
> >>
> >>> This also should be built on linux only.
> >>
> >> Why, what do we gain with #ifdefs? And isn't the addressing concept generic?
> > 
> > Not the XXX:XX.X format. And not the concept of a domain.
> > 
> >>> Can this be part of device assignment code instead of qdev?
> >>
> >> How does VFIO address their host devices?
> > 
> > You get an fd I think. I think you don't need to know the host address.
> 
> vfio_pci.c contains a nice function called "parse_hostaddr". You may
> guess what it does. ;)

Interesting. Why? This looks strange to me:
I would expect the admin to bind a device to vfio
the way it's now bound to a stub.
The pass /dev/vfioXXX to qemu.

> 
> So we need this generic service. Let's called it pci-host-devaddr and be
> fine?
> 
> Jan
>