Re: [Qemu-devel] Headsup: windows virtio networking does not work on current git

[Yan Vugenfirer]

On Feb 7, 2013, at 1:46 PM, Vadim Rozenfeld wrote:

> On Thu, 2013-02-07 at 13:33 +0200, Michael S. Tsirkin wrote:
>> On Thu, Feb 07, 2013 at 09:53:39PM +1100, Vadim Rozenfeld wrote:
>>> On Thu, 2013-02-07 at 12:18 +0200, Michael S. Tsirkin wrote:
>>>> On Thu, Feb 07, 2013 at 08:24:10PM +1100, Vadim Rozenfeld wrote:
>>>>> On Thu, 2013-02-07 at 11:33 +1030, Rusty Russell wrote:
>>>>>> Vadim Rozenfeld <address@hidden> writes:
>>>>>>> On Tue, 2013-02-05 at 13:58 +0200, Michael S. Tsirkin wrote:
>>>>>>>> On Tue, Feb 05, 2013 at 03:45:38PM +0400, Michael Tokarev wrote:
>>>>>>>> Is it really
>>>>>>>>> that bad that the config space size changed?  Why it has this effect?
>>>>>>> Because in this case it's hard to distinguish between resource's
>>>>>>> corruption and HW update.
>>>>>> 
>>>>>> But it's also true that if we'd incremented revid you'd have the same
>>>>>> failure in this case, right?
>>>>> 
>>>>> It depends. If we have explicitly specified revision id in inf file and
>>>>> this id doesn't mach the new revision id, Windows will not try to load
>>>>> the "incompatible" driver, and finish up with "device driver not found"
>>>>> dialog.
>>>>> 
>>>>> Best regards,
>>>>> Vadim.
>>>>> 
>>>>>> 
>>>>>> Cheers,
>>>>>> Rusty.
>>>> 
>>>> Well that's all in theory, in practice it does not look like revision ID
>>>> is specified in the NetKVM inf so this won't work?
>>>> 
>>>> From what I see this inf specifies:
>>>> 
>>>> NetKVM/wlh/netkvm.inf:%kvmnet6.DeviceDesc%    = kvmnet6.ndi, 
>>>> PCI\VEN_1AF4&DEV_1000&SUBSYS_00011AF4
>>>> NetKVM/wxp/netkvm.inf:%kvmnet5.DeviceDesc%    = kvmnet5.ndi, 
>>>> PCI\VEN_1AF4&DEV_1000&SUBSYS_00011AF4
>>>> NetKVM/wxp/netkvm2k.inf:%kvmnet5.DeviceDesc%    = kvmnet5.ndi, 
>>>> PCI\VEN_1AF4&DEV_1000&SUBSYS_00011AF4
>>>> 
>>>> So we can tweak any of vendor device and subsystem id.
>>>> 
>>> Unfortunately, it won't. Only balloon has revision id, specified as a
>>> part of device HW descriptor. But it's only because virtio doesn't use 
>>> revision ids. Otherwise it differential will be there. 
>> 
>> So your driver will load and attempt to work on rev=2 devices?
> 
> All virtio-win drivers (net, serial, block, and scsi), except for
> balloon will.
> 
>> If yes it's a bug.  virtio spec specifies revision id as an ABI version.
>> Linux driver does:
>> 
>>        if (pci_dev->revision != VIRTIO_PCI_ABI_VERSION) {
>>                printk(KERN_ERR "virtio_pci: expected ABI version %d, got 
>> %d\n",
>>                       VIRTIO_PCI_ABI_VERSION, pci_dev->revision);
>>                return -ENODEV;
>>        }
>> 

We can add it from next release. Provided that everyone understand the 
consequences especially for boot devices (virtio-block and virtio-scsi).


>> 
>>>> 
>>>> Changing subsystem vendor ID actually will be completely
>>>> transparent to linux which for some reason looks at the
>>>> subsystem device ID (why? no idea) but not the subsystem vendor ID.
>>>> Of course this requires a valid vendor ID, getting this
>>>> costs $3000 I think.
>>>> We could tweak device ID too but that might break some other guests
>>>> which don't copy the crazy 'replace device id with subsystem device id'
>>>> logic from Linux.
>>>> 
>>> 
>> 
>> Apropos, would you guys like to start to copy your patches to
>> address@hidden
>> If you do, you might get some review and feedback, allowing
>> us to catch such forward compatibility issues earlier.
>> 
>> Of course it's your project so entirely up to you.
>> 
>> 
> 
>