Re: [Qemu-devel] [PATCH] Remove PCI class code from virtio balloon device

[Anthony Liguori <anthony@codemonkey.ws>]

On 03/21/2012 10:10 AM, Michael S. Tsirkin wrote:
> On Wed, Mar 21, 2012 at 09:42:41AM -0500, Anthony Liguori wrote:
>> On 03/21/2012 08:08 AM, Michael S. Tsirkin wrote:
>>> On Wed, Mar 21, 2012 at 11:26:15AM +0000, Stefan Hajnoczi wrote:
>>>> On Tue, Mar 20, 2012 at 09:19:47PM +1100, David Gibson wrote:
>>>> Looking at hw/pc_piix.c there are QEMUMachine types for each QEMU
>>>> release.  Legacy machine types (e.g. pc_machine_v0_14) have a
>>>> .compat_props array that can override qdev properties.
>>>>
>>>> Perhaps Michael Tsirkin or someone else can comment on how to wire up
>>>> hw/virtio-pci.c so that the class code can be overridden.
>>>>
>>>> Stefan
>>>
>>> afaik we already let users over-write it for some other pci devices,
>>> look there for examples.
>>
>>  From hw/pc_piix.c:
>>
>>      .name = "pc-0.10",
>>      .desc = "Standard PC, qemu 0.10",
>>      .init = pc_init_pci_no_kvmclock,
>>      .max_cpus = 255,
>>      .compat_props = (GlobalProperty[]) {
>>          {
>>              .driver   = "virtio-blk-pci",
>>              .property = "class",
>>              .value    = stringify(PCI_CLASS_STORAGE_OTHER),
>>          },{
>>
>> And from the earlier part of the thread, yes, it's imperative that
>> we do not change anything in the PCI configuration space for older
>> pc versions regardless of whether it may or may not work.
>>
>> Certain guests (like Windows) use a complex fingerprinting algorithm
>> to determine when hardware changes.  It can be hard to detect in
>> simple testing because it's based on a threshold.
>>
>> Regards,
>>
>> Anthony Liguori
>
> Which reminds me - qemu sticks the release version in
> guest visible places like CPU version.
> This is wrong and causes windows guests to print messages
> about driver updates when you switch.
> We should find all these places and stop doing this.

We could probably get away with doing a query/replace of QEMU_VERSION with 
qemu_get_version(), make version a static variable that defaults to 
QEMU_VERSION, and then provide a way for machines to override it.

Then pc-0.10 could report a version of 0.10.

Regards,

Anthony Liguori

>>>
>>>