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

[Bernhard Beschow <shentey@xxxxxxxxx>]

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!

Best regards,
Bernhard

>I get the exact same output from lspci without the patch series, so that gives
>me confidence it is working as designed.