Re: [PATCH v2 6/6] hw/isa/piix: Resolve redundant TYPE_PIIX3_XEN_DEVICE

[Bernhard Beschow]

Am 7. Januar 2023 01:08:46 UTC schrieb Chuck Zmudzinski <brchuckz@aol.com>:
>On 1/6/23 6:04 PM, Chuck Zmudzinski wrote:
>> On 1/6/23 2:08 PM, Chuck Zmudzinski wrote:
>>> On 1/6/23 7:25 AM, Philippe Mathieu-Daudé wrote:
>>>> On 6/1/23 12:57, Bernhard Beschow wrote:
>>>>> 
>>>>> 
>>>>> Am 4. Januar 2023 15:35:33 UTC schrieb "Philippe Mathieu-Daudé" 
>>>>> <philmd@linaro.org>:
>>>>>> +Markus/Thomas
>>>>>>
>>>>>> On 4/1/23 15:44, Bernhard Beschow wrote:
>>>>>>> During the last patches, TYPE_PIIX3_XEN_DEVICE turned into a clone of
>>>>>>> TYPE_PIIX3_DEVICE. Remove this redundancy.
>>>>>>>
>>>>>>> Signed-off-by: Bernhard Beschow <shentey@gmail.com>
>>>>>>> ---
>>>>>>>    hw/i386/pc_piix.c             |  4 +---
>>>>>>>    hw/isa/piix.c                 | 20 --------------------
>>>>>>>    include/hw/southbridge/piix.h |  1 -
>>>>>>>    3 files changed, 1 insertion(+), 24 deletions(-)
>>>> 
>>>> 
>>>>>>>    -static void piix3_xen_class_init(ObjectClass *klass, void *data)
>>>>>>> -{
>>>>>>> -    DeviceClass *dc = DEVICE_CLASS(klass);
>>>>>>> -    PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
>>>>>>> -
>>>>>>> -    k->realize = piix3_realize;
>>>>>>> -    /* 82371SB PIIX3 PCI-to-ISA bridge (Step A1) */
>>>>>>> -    k->device_id = PCI_DEVICE_ID_INTEL_82371SB_0;
>>>>>>> -    dc->vmsd = &vmstate_piix3;
>>>>>>
>>>>>> IIUC, since this device is user-creatable, we can't simply remove it
>>>>>> without going thru the deprecation process.
>>>>> 
>>>>> AFAICS this device is actually not user-creatable since 
>>>>> dc->user_creatable is set to false once in the base class. I think it is 
>>>>> safe to remove the Xen class unless there are ABI issues.
>>>> Great news!
>>> 
>>> I don't know if this means the device is user-creatable:
>>> 
>>> chuckz@bullseye:~$ qemu-system-i386 -device piix3-ide-xen,help
>>> piix3-ide-xen options:
>>>   addr=<int32>           - Slot and optional function number, example: 06.0 
>>> or 06 (default: -1)
>>>   failover_pair_id=<str>
>>>   multifunction=<bool>   - on/off (default: false)
>>>   rombar=<uint32>        -  (default: 1)
>>>   romfile=<str>
>>>   x-pcie-extcap-init=<bool> - on/off (default: true)
>>>   x-pcie-lnksta-dllla=<bool> - on/off (default: true)
>>> 
>>> Today I am running qemu-5.2 on Debian 11, so this output is for
>>> qemu 5.2, and that version of qemu has a piix3-ide-xen device.
>>> Is that this same device that is being removed? If so, it seems to
>>> me that at least as of qemu 5.2, the device was user-creatable.
>>> 
>>> Chuck
>> 
>> Good news! It looks the device was removed as user-creatable since version 
>> 5.2:
>> 
>> chuckz@debian:~$ qemu-system-i386-7.50 -device help | grep piix
>> name "piix3-usb-uhci", bus PCI
>> name "piix4-usb-uhci", bus PCI
>> name "piix3-ide", bus PCI
>> name "piix4-ide", bus PCI
>> chuckz@debian:~$ qemu-system-i386-7.50-bernhard-v2 -device help | grep piix
>> name "piix3-usb-uhci", bus PCI
>> name "piix4-usb-uhci", bus PCI
>> name "piix3-ide", bus PCI
>> name "piix4-ide", bus PCI
>> chuckz@debian:~$
>> 
>> The piix3-ide-xen device is not present either with or without Bernhard's 
>> patches
>> for current qemu 7.50, the development version for qemu 8.0
>> 
>> Cheers,
>> 
>> Chuck
>
>
>I traced where the pciix3-ide-xen device was removed:
>
>It was 7851b21a81 (hw/ide/piix: Remove redundant "piix3-ide-xen" device class)
>
>https://gitlab.com/qemu-project/qemu/-/commit/7851b21a8192750adecbcf6e8780a20de5891ad6
>
>about six months ago. That was between 7.0 and 7.1. So the device being removed
>here is definitely not user-creatable, but it appears that this piix3-ide-xen
>device that was removed between 7.0 and 7.1 was user-creatable. Does that one
>need to go through the deprecation process? Or, since no one has complained
>it is gone, maybe we don't need to worry about it?

Good point! Looks like it fell through the cracks...

There are voices who claim that this device and its non-Xen counterpart should 
have never been user-creatable in the firtst place:
https://patchwork.kernel.org/project/qemu-devel/patch/20190718091740.6834-1-philmd@redhat.com/

Best regards,
Bernhard

>
>Cheers,
>
>Chuck