[Qemu-devel] [PATCH] spapr-pci: remove io ports workaround

[Greg Kurz <gkurz@linux.vnet.ibm.com>]

In the past, IO space could not be mapped into the memory address space
so we introduced a workaround for that. Nowadays it does not look
necessary so we can remove the workaround and make sPAPR PCI
configuration simplier.

This workaround has also an evil side effect with virtio devices: because
all PHBs have their .io region at the same address, the devices
get mapped in the .io-alias region of every PHB (AKA. mapped multiple times).
This breaks the ioeventfd feature and causes qemu to abort() when running
with KVM and asking for more than one PHB:

$ qemu-system-ppc64 -machine type=pseries,accel=kvm -smp 1 -m 4G \
  -hda /local/greg/images/fedora-be.qcow2 \
  -device virtio-9p-pci,fsdev=fsdev0,mount_tag=share,bus=pci,ioeventfd=on \
  -fsdev local,security_model=none,id=fsdev0,path=$HOME/share1 \
  -device spapr-pci-host-bridge,index=15
kvm_mem_ioeventfd_add: error adding ioeventfd: File exists
Aborted

This will prevent to use virtio and VFIO passthrough at the same time, since
VFIO needs a dedicated PHB to work on ppc.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
 hw/ppc/spapr_pci.c |   13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index 7763149..7d29431 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -564,23 +564,14 @@ static int spapr_phb_init(SysBusDevice *s)
     memory_region_add_subregion(get_system_memory(), sphb->mem_win_addr,
                                 &sphb->memwindow);
 
-    /* On ppc, we only have MMIO no specific IO space from the CPU
-     * perspective.  In theory we ought to be able to embed the PCI IO
-     * memory region direction in the system memory space.  However,
-     * if any of the IO BAR subregions use the old_portio mechanism,
-     * that won't be processed properly unless accessed from the
-     * system io address space.  This hack to bounce things via
-     * system_io works around the problem until all the users of
-     * old_portion are updated */
+    /* Initialize IO regions */
     sprintf(namebuf, "%s.io", sphb->dtbusname);
     memory_region_init(&sphb->iospace, OBJECT(sphb),
                        namebuf, SPAPR_PCI_IO_WIN_SIZE);
-    /* FIXME: fix to support multiple PHBs */
-    memory_region_add_subregion(get_system_io(), 0, &sphb->iospace);
 
     sprintf(namebuf, "%s.io-alias", sphb->dtbusname);
     memory_region_init_alias(&sphb->iowindow, OBJECT(sphb), namebuf,
-                             get_system_io(), 0, SPAPR_PCI_IO_WIN_SIZE);
+                             &sphb->iospace, 0, SPAPR_PCI_IO_WIN_SIZE);
     memory_region_add_subregion(get_system_memory(), sphb->io_win_addr,
                                 &sphb->iowindow);
     /*