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

[Jan Kiszka]

On 2012-06-10 12:58, Michael S. Tsirkin wrote:
> 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 <address@hidden>
>>>>>
>>>>> 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.

That's the "libvirt way". We surely also want the "qemu command line
way" for which this kind of service is needed.

Jan

signature.asc
Description: OpenPGP digital signature