[Qemu-devel] Re: [PATCH] piix: use pci_config_set_prog_interface()

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

On Wed, Dec 29, 2010 at 11:26:32AM +0100, Sebastian Herbszt wrote:
> Michael S. Tsirkin wrote:
> >On Tue, Dec 28, 2010 at 07:48:23PM +0100, Sebastian Herbszt wrote:
> >>Michael S. Tsirkin wrote:
> >>>On Tue, Dec 28, 2010 at 05:24:06PM +0100, Sebastian Herbszt wrote:
> >>>>Michael S. Tsirkin wrote:
> >>>>>On Mon, Dec 20, 2010 at 10:18:01PM +0100, Sebastian Herbszt wrote:
> >>>>>>Use pci_config_set_prog_interface().
> >>>>>>
> >>>>>>Signed-off-by: Sebastian Herbszt <herbszt@gmx.de>
> >>>>>
> >>>>>Since I was asked explicitly - I don't have a problem
> >>>>>with these changes: both class and prog interface.
> >>>>>However, they aren't all that useful in themselves.
> >>>>>
> >>>>>For class, what I would like to see is a system where
> >>>>>the device class is put in the qdev info table,
> >>>>>and where -device ?
> >>>>>(and hopefully the legacy -help, -nic etc as well)
> >>>>>use this information.
> >>>>
> >>>>I am not sure if you mean something like the patch below.
> >>>
> >>>Not exactly
> >>>
> >>>- I'd like to keep the pci_config_set_class in the devices,
> >>> just make it do an assert.
> >>
> >>Assert on which condition?
> >
> >That PCI class matches device type defined in qdev.
> >This will serve to verify that all devices are converted properly.
> >
> >>>- Nics already have DEFINE_NIC_PROPERTIES - can this be used somehow?
> >>> Same for other devices ...
> >>
> >>We got DEFINE_NIC_PROPERTIES and DEFINE_BLOCK_PROPERTIES.
> >>Something like DEFINE_PCI_PROPERTIES could be introduced, but i am not sure
> >
> >This shouldn't have to do anything with PCI.
> >We should define the device type as NIC,
> >PCI class can be derived from that.
> 
> So you want to introduce a device property like "device_type" and set it to "NIC" and
> then translate "NIC" to the correct PCI class code. Are you sure this is unambiguous?

It does not need to be, that's why I would like to keep the
code in device init that sets the PCI class.
We would just check that it matches.

> "NIC" could be ethernet or token ring. A generic name like "HBA" could translate to even
> more codes (scsi, ide, raid, sata, ...).

I don't insist on NIC. Maybe ethernet is a good thing.
Maybe pci_class_descriptions is a good starting point.

> 
> >>which device properties it should hold (vendor_id, device_id, class, etc?).
> >>Those will then be user-modifiable with e.g. -device e1000,pci_class=1234.
> >>
> >>Sebastian
> >
> >Why is this helpful?
> >- tweaking class will just break guests
> >- binary representation is unfriendly, let's not require users to read
> > pci spec just to run qemu.
> 
> "pci_class" is optional. I just wanted to show that qdev device properties are
> user-modifiable and i didn't find a way to prevent this.
> 
> >I can imagine some useful features implemented by sticking the type in qdev:
> >- -device ? would sort devices by type and print the type,
> >- something like this for qtree etc
> >- -help would get all e.g. nic models from qdev,
> >-  allow easy to remember aliases with per-type scope (e.g.
> >  -device virtio,type=nic to be equivalent to -device virtio-net-pci)
> 
> Is this just a virtio problem?

Not sure. I think usb has this, I think there are others.

> >- filter (for device ?, qtree etc) system devices that user has no business
> >  tweaking (could be type=system or something like that)
> >
> >>diff --git a/hw/e1000.c b/hw/e1000.c
> >>index af101bd..e302703 100644
> >>--- a/hw/e1000.c
> >>+++ b/hw/e1000.c
> >>@@ -1171,6 +1171,7 @@ static PCIDeviceInfo e1000_info = {
> >>    .romfile    = "pxe-e1000.bin",
> >>    .qdev.props = (Property[]) {
> >>        DEFINE_NIC_PROPERTIES(E1000State, conf),
> >>+        DEFINE_PROP_UINT16("pci_class", E1000State, dev.class, PCI_CLASS_NETWORK_ETHERNET),
> >>        DEFINE_PROP_END_OF_LIST(),
> >>    }
> >>};
> >>diff --git a/hw/pci.c b/hw/pci.c
> >>index ef00d20..06bbf04 100644
> >>--- a/hw/pci.c
> >>+++ b/hw/pci.c
> >>@@ -1620,6 +1620,9 @@ static int pci_qdev_init(DeviceState *qdev, DeviceInfo *base)
> >>                                     info->is_bridge);
> >>    if (pci_dev == NULL)
> >>        return -1;
> >>+
> >>+    pci_config_set_class(pci_dev->config, pci_dev->class);
> >>+
> >>    rc = info->init(pci_dev);
> >>    if (rc != 0) {
> >>        do_pci_unregister_device(pci_dev);
> >>diff --git a/hw/pci.h b/hw/pci.h
> >>index 17744dc..5dc9053 100644
> >>--- a/hw/pci.h
> >>+++ b/hw/pci.h
> >>@@ -189,6 +189,9 @@ struct PCIDevice {
> >>    char *romfile;
> >>    ram_addr_t rom_offset;
> >>    uint32_t rom_bar;
> >>+
> >>+    /* class */
> >
> >Please don't copy code into comments verbatim.
> >
> >>+    uint16_t class;
> >
> >Ugh. We have class in config already.
> 
> But i could not get qdev to use it.

That's a problem for qdev to solve :)

> >>};
> >>
> >>PCIDevice *pci_register_device(PCIBus *bus, const char *name,
> >>
> 
> Sebastian