Re: [Qemu-devel] [PATCH] spapr_pci: turn IOMMU root into an I/O region

[Alexander Graf <agraf@suse.de>]

On 26.08.14 18:40, Greg Kurz wrote:
> On sPAPR, virtio devices are connected to the PCI bus and use MSI-X.
> Commit cc943c36faa192cd4b32af8fe5edb31894017d35 has modified MSI-X
> so that writes are made using the bus master address space.
> Unfortunately, the MSI-X notification hits unassigned_mem_write and
> never reaches the guest... The most visible effect is that all
> virtio devices are non-fonctionnal on sPAPR. :(
> 
> This patch plugs the MSI memory ops to the root IOMMU region, and
> virtio devices work again. I am not sure this is the right way to
> fix: please comment and enlight !
> 
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr_pci.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index 9ed39a9..b638a3c 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -599,8 +599,9 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
>       */
>      sprintf(namebuf, "%s.iommu-root", sphb->dtbusname);
>  
> -    memory_region_init(&sphb->iommu_root, OBJECT(sphb),
> -                       namebuf, UINT64_MAX);
> +    memory_region_init_io(&sphb->iommu_root, OBJECT(sphb),
> +                          &spapr_msi_ops, spapr,
> +                          namebuf, UINT64_MAX);

This will turn all unallocated accesses in iommu_root into calls to
spapr_msi_ops, no?

Can't we instead just populate the iommu_root memory region with the MSI
subregion?


Alex