On 04/02/2026 06:29, Michael S. Tsirkin wrote:
On Mon, Nov 24, 2025 at 12:47:54PM +0100, Philippe Mathieu-Daudé wrote:
Before commit 3716d5902d7 ("pci: introduce a bus master container")
device view of the bus address space was correctly sized to the
bus aperture, but then it always used a 64-bit aperture. Restore
the previous behavior, so devices on 32-bit PCI only see 32-bit
address space.
Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Wait I am confused. Is there a problem this is trying to fix?
---
hw/pci/pci.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index b1eba348e06..64f33b9de04 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -1375,7 +1375,8 @@ static PCIDevice *do_pci_register_device(PCIDevice
*pci_dev,
pstrcpy(pci_dev->name, sizeof(pci_dev->name), name);
memory_region_init(&pci_dev->bus_master_container_region, OBJECT(pci_dev),
- "bus master container", UINT64_MAX);
+ "bus master container",
+ memory_region_size(bus->address_space_mem));
as far as I can tell this does more than it says it does.
Look at raven.c:
h->bus = pci_register_root_bus(d, NULL, raven_set_irq, raven_map_irq,
s, &s->pci_memory, &s->pci_io, 0, 4,
TYPE_PCI_BUS);
The bus is created with &s->pci_memory (1G) as the address space.
But the actual bus master space (&s->bm at line 285) is 4 G.
Your patch limits DMA to 1G. No?
failures here (definitely the ppc one)
https://gitlab.com/mstredhat/qemu/-/jobs/12984084992
reverting fixed it:
https://gitlab.com/mstredhat/qemu/-/jobs/12984187692
Thanks for the catch, Michael.
Sorry, I wasn't aware of this quirk in raven when I acked. Looking into
it now, it seems that prior to 97db0466788 its pci_memory had size
0xff000000 as a workaround, and that would indeed "fix" the regression
here, too, but is probably not preferable to leaving the bus master
container maxed out. What do you think, Philippe?
address_space_init(&pci_dev->bus_master_as,
&pci_dev->bus_master_container_region, pci_dev->name);
pci_dev->bus_master_as.max_bounce_buffer_size =
--
2.51.0
