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

[Chuck Zmudzinski <brchuckz@xxxxxxx>]

On 1/4/23 3:31 PM, Bernhard Beschow wrote:
> 
> 
> Am 4. Januar 2023 19:29:35 UTC schrieb Chuck Zmudzinski <brchuckz@xxxxxxx>:
>>On 1/4/23 1:48 PM, Philippe Mathieu-Daudé wrote:
>>> On 4/1/23 18:54, Chuck Zmudzinski wrote:
>>>> On 1/4/23 10:35 AM, Philippe Mathieu-Daudé wrote:
>>>>> +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@xxxxxxxxx>
>>>>>> ---
>>>>>>    hw/i386/pc_piix.c             |  4 +---
>>>>>>    hw/isa/piix.c                 | 20 --------------------
>>>>>>    include/hw/southbridge/piix.h |  1 -
>>>>>>    3 files changed, 1 insertion(+), 24 deletions(-)
>>>>>>
>>>>>> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
>>>>>> index 5738d9cdca..6b8de3d59d 100644
>>>>>> --- a/hw/i386/pc_piix.c
>>>>>> +++ b/hw/i386/pc_piix.c
>>>>>> @@ -235,8 +235,6 @@ static void pc_init1(MachineState *machine,
>>>>>>        if (pcmc->pci_enabled) {
>>>>>>            DeviceState *dev;
>>>>>>            PCIDevice *pci_dev;
>>>>>> -        const char *type = xen_enabled() ? TYPE_PIIX3_XEN_DEVICE
>>>>>> -                                         : TYPE_PIIX3_DEVICE;
>>>>>>            int i;
>>>>>>    
>>>>>>            pci_bus = i440fx_init(pci_type,
>>>>>> @@ -250,7 +248,7 @@ static void pc_init1(MachineState *machine,
>>>>>>                                           : pci_slot_get_pirq);
>>>>>>            pcms->bus = pci_bus;
>>>>>>    
>>>>>> -        pci_dev = pci_new_multifunction(-1, true, type);
>>>>>> +        pci_dev = pci_new_multifunction(-1, true, TYPE_PIIX3_DEVICE);
>>>>>>            object_property_set_bool(OBJECT(pci_dev), "has-usb",
>>>>>>                                     machine_usb(machine), &error_abort);
>>>>>>            object_property_set_bool(OBJECT(pci_dev), "has-acpi",
>>>>>> diff --git a/hw/isa/piix.c b/hw/isa/piix.c
>>>>>> index 98e9b12661..e4587352c9 100644
>>>>>> --- a/hw/isa/piix.c
>>>>>> +++ b/hw/isa/piix.c
>>>>>> @@ -33,7 +33,6 @@
>>>>>>    #include "hw/qdev-properties.h"
>>>>>>    #include "hw/ide/piix.h"
>>>>>>    #include "hw/isa/isa.h"
>>>>>> -#include "hw/xen/xen.h"
>>>>>>    #include "sysemu/runstate.h"
>>>>>>    #include "migration/vmstate.h"
>>>>>>    #include "hw/acpi/acpi_aml_interface.h"
>>>>>> @@ -465,24 +464,6 @@ static const TypeInfo piix3_info = {
>>>>>>        .class_init    = piix3_class_init,
>>>>>>    };
>>>>>>    
>>>>>> -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. Alternatively we could
>>>>> add a type alias:
>>>>>
>>>>> -- >8 --
>>>>> diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c
>>>>> index 4b0ef65780..d94f7ea369 100644
>>>>> --- a/softmmu/qdev-monitor.c
>>>>> +++ b/softmmu/qdev-monitor.c
>>>>> @@ -64,6 +64,7 @@ typedef struct QDevAlias
>>>>>                                  QEMU_ARCH_LOONGARCH)
>>>>>    #define QEMU_ARCH_VIRTIO_CCW (QEMU_ARCH_S390X)
>>>>>    #define QEMU_ARCH_VIRTIO_MMIO (QEMU_ARCH_M68K)
>>>>> +#define QEMU_ARCH_XEN (QEMU_ARCH_ARM | QEMU_ARCH_I386)
>>>>>
>>>>>    /* Please keep this table sorted by typename. */
>>>>>    static const QDevAlias qdev_alias_table[] = {
>>>>> @@ -111,6 +112,7 @@ static const QDevAlias qdev_alias_table[] = {
>>>>>        { "virtio-tablet-device", "virtio-tablet", QEMU_ARCH_VIRTIO_MMIO },
>>>>>        { "virtio-tablet-ccw", "virtio-tablet", QEMU_ARCH_VIRTIO_CCW },
>>>>>        { "virtio-tablet-pci", "virtio-tablet", QEMU_ARCH_VIRTIO_PCI },
>>>>> +    { "PIIX3", "PIIX3-xen", QEMU_ARCH_XEN },
>>>> 
>>>> Hi Bernhard,
>>>> 
>>>> Can you comment if this should be:
>>>> 
>>>> +    { "PIIX", "PIIX3-xen", QEMU_ARCH_XEN },
>>>> 
>>>> instead? IIUC, the patch series also removed PIIX3 and PIIX4 and
>>>> replaced them with PIIX. Or am I not understanding correctly?
>>> 
>>> There is a confusion in QEMU between PCI bridges, the first PCI
>>> function they implement, and the other PCI functions.
>>> 
>>> Here TYPE_PIIX3_DEVICE means for "PCI function part of the PIIX
>>> south bridge chipset, which expose a PCI-to-ISA bridge". A better
>>> name could be TYPE_PIIX3_ISA_PCI_DEVICE. Unfortunately this
>>> device is named "PIIX3" with no indication of ISA bridge.
>>
>>
>>Thanks, you are right, I see the PIIX3 device still exists after
>>this patch set is applied.
>>
>>chuckz@debian:~/sources-sid/qemu/qemu-7.50+dfsg/hw/i386$ grep -r PIIX3 *
>>pc_piix.c:        pci_dev = pci_new_multifunction(-1, true, 
>>TYPE_PIIX3_DEVICE);
>>
>>I also understand there is the PCI-to-ISA bridge at 00:01.0 on the PCI bus:
>>
>>chuckz@debian:~$ lspci
>>00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
>>00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
>>00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
>>00:01.2 USB controller: Intel Corporation 82371SB PIIX3 USB [Natoma/Triton 
>>II] (rev 01)
>>00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
>>00:02.0 Unassigned class [ff80]: XenSource, Inc. Xen Platform Device (rev 01)
>>00:03.0 VGA compatible controller: Device 1234:1111 (rev 02)
>>
>>I also see with this patch, there is a bridge that is a PIIX4 ACPI at 00:01.3.
> 
> Yeah, this PIIX4 ACPI device is what we consider a "Frankenstein" device here 
> on the list. Indeed my PIIX consolidation series aims for eventually 
> replacing the remaining PIIX3 devices with PIIX4 ones to present a realistic 
> environment to guests. The series you tested makes Xen work with PIIX4. With 
> a couple of more patches you might be able to opt into a realistic PIIX4 
> emulation in the future!

That's exactly what I want to hear as a future milestone, and thanks
for your work on this!

Kind regards,

Chuck