[PATCH] hw/pci-host/sabre: Mark unusable PCI busses as full to ease device plugging

[PATCH] hw/pci-host/sabre: Mark unusable PCI busses as full to ease device plugging

[Thomas Huth]

From: Thomas Huth <thuth@redhat.com>

When trying to plug a PCI device to a Sparc64 machine, you currently
have to specify the right bus ("bus=pciB"), otherwise you get this error:

 $ qemu-system-sparc64 -device virtio-scsi-pci
 qemu-system-sparc64: -device virtio-scsi-pci: PCI: no slot/function
  available for virtio-scsi-pci, all in use or reserved

This is quite annoying for the unexperienced users, and it also breaks
e.g. the iotests ("make check-block") when running with qemu-system-sparc64.

Mark the non-usable PCI busses as full now, so that QEMU can automatically
plug new PCI devices to the right "pciB" bus.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 Note: Only lightly tested, it seems to work fine for me at a first glance,
 but maybe I missed something...

 hw/pci-host/sabre.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/pci-host/sabre.c b/hw/pci-host/sabre.c
index cd2328ad53f..9c8519f3849 100644
--- a/hw/pci-host/sabre.c
+++ b/hw/pci-host/sabre.c
@@ -382,6 +382,7 @@ static void sabre_realize(DeviceState *dev, Error **errp)
                                      &s->pci_mmio,
                                      &s->pci_ioport,
                                      0, 0x40, TYPE_PCI_BUS);
+    qbus_mark_full(&phb->bus->qbus);
 
     pci_create_simple(phb->bus, 0, TYPE_SABRE_PCI_DEVICE);
 
@@ -400,6 +401,7 @@ static void sabre_realize(DeviceState *dev, Error **errp)
     s->bridgeA = PCI_BRIDGE(pci_dev);
     pci_bridge_map_irq(s->bridgeA, "pciA", pci_simbaA_map_irq);
     pci_realize_and_unref(pci_dev, phb->bus, &error_fatal);
+    qbus_mark_full(&s->bridgeA->sec_bus.qbus);
 }
 
 static void sabre_init(Object *obj)
-- 
2.53.0

Re: [PATCH] hw/pci-host/sabre: Mark unusable PCI busses as full to ease device plugging

[Mark Cave-Ayland]

On 16/02/2026 15:49, Thomas Huth wrote:

> From: Thomas Huth <thuth@redhat.com>
> 
> When trying to plug a PCI device to a Sparc64 machine, you currently
> have to specify the right bus ("bus=pciB"), otherwise you get this error:
> 
>   $ qemu-system-sparc64 -device virtio-scsi-pci
>   qemu-system-sparc64: -device virtio-scsi-pci: PCI: no slot/function
>    available for virtio-scsi-pci, all in use or reserved
> 
> This is quite annoying for the unexperienced users, and it also breaks
> e.g. the iotests ("make check-block") when running with qemu-system-sparc64.
> 
> Mark the non-usable PCI busses as full now, so that QEMU can automatically
> plug new PCI devices to the right "pciB" bus.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   Note: Only lightly tested, it seems to work fine for me at a first glance,
>   but maybe I missed something...
> 
>   hw/pci-host/sabre.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/hw/pci-host/sabre.c b/hw/pci-host/sabre.c
> index cd2328ad53f..9c8519f3849 100644
> --- a/hw/pci-host/sabre.c
> +++ b/hw/pci-host/sabre.c
> @@ -382,6 +382,7 @@ static void sabre_realize(DeviceState *dev, Error **errp)
>                                        &s->pci_mmio,
>                                        &s->pci_ioport,
>                                        0, 0x40, TYPE_PCI_BUS);
> +    qbus_mark_full(&phb->bus->qbus);
>   
>       pci_create_simple(phb->bus, 0, TYPE_SABRE_PCI_DEVICE);
>   
> @@ -400,6 +401,7 @@ static void sabre_realize(DeviceState *dev, Error **errp)
>       s->bridgeA = PCI_BRIDGE(pci_dev);
>       pci_bridge_map_irq(s->bridgeA, "pciA", pci_simbaA_map_irq);
>       pci_realize_and_unref(pci_dev, phb->bus, &error_fatal);
> +    qbus_mark_full(&s->bridgeA->sec_bus.qbus);
>   }
>   
>   static void sabre_init(Object *obj)

Apologies for the delay on this: I think the patch makes logical sense, however the 
existing logic to manage the available PCI slots is handled in sun4uv_init(). Do you 
think it makes sense to move the qbus_mark_full() calls to the same place?


ATB,

Mark.

Re: [PATCH] hw/pci-host/sabre: Mark unusable PCI busses as full to ease device plugging

[Thomas Huth]

On 09/03/2026 00.06, Mark Cave-Ayland wrote:
> On 16/02/2026 15:49, Thomas Huth wrote:
> 
>> From: Thomas Huth <thuth@redhat.com>
>>
>> When trying to plug a PCI device to a Sparc64 machine, you currently
>> have to specify the right bus ("bus=pciB"), otherwise you get this error:
>>
>>   $ qemu-system-sparc64 -device virtio-scsi-pci
>>   qemu-system-sparc64: -device virtio-scsi-pci: PCI: no slot/function
>>    available for virtio-scsi-pci, all in use or reserved
>>
>> This is quite annoying for the unexperienced users, and it also breaks
>> e.g. the iotests ("make check-block") when running with qemu-system-sparc64.
>>
>> Mark the non-usable PCI busses as full now, so that QEMU can automatically
>> plug new PCI devices to the right "pciB" bus.
>>
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>> ---
>>   Note: Only lightly tested, it seems to work fine for me at a first glance,
>>   but maybe I missed something...
>>
>>   hw/pci-host/sabre.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/hw/pci-host/sabre.c b/hw/pci-host/sabre.c
>> index cd2328ad53f..9c8519f3849 100644
>> --- a/hw/pci-host/sabre.c
>> +++ b/hw/pci-host/sabre.c
>> @@ -382,6 +382,7 @@ static void sabre_realize(DeviceState *dev, Error **errp)
>>                                        &s->pci_mmio,
>>                                        &s->pci_ioport,
>>                                        0, 0x40, TYPE_PCI_BUS);
>> +    qbus_mark_full(&phb->bus->qbus);
>>       pci_create_simple(phb->bus, 0, TYPE_SABRE_PCI_DEVICE);
>> @@ -400,6 +401,7 @@ static void sabre_realize(DeviceState *dev, Error **errp)
>>       s->bridgeA = PCI_BRIDGE(pci_dev);
>>       pci_bridge_map_irq(s->bridgeA, "pciA", pci_simbaA_map_irq);
>>       pci_realize_and_unref(pci_dev, phb->bus, &error_fatal);
>> +    qbus_mark_full(&s->bridgeA->sec_bus.qbus);
>>   }
>>   static void sabre_init(Object *obj)
> 
> Apologies for the delay on this: I think the patch makes logical sense, 
> however the existing logic to manage the available PCI slots is handled in 
> sun4uv_init(). Do you think it makes sense to move the qbus_mark_full() 
> calls to the same place?

That makes sense, indeed! I'll send a v2...

  Thomas