Re: [Qemu-devel] [PATCH] virtio: unbreak virtio-pci with IOMMU after caching ring translations

[Jason Wang]

On 2017年03月02日 13:10, Michael S. Tsirkin wrote:
> On Wed, Mar 01, 2017 at 12:10:40PM +0800, Jason Wang wrote:
> > Commit c611c76417f5 ("virtio: add MemoryListener to cache ring
> > translations") registers a memory listener to dma_as. This may not
> > work when IOMMU is enabled: dma_as(bus_master_as) were initialized in
> > pcibus_machine_done() after virtio_realize(). This will cause a
> > segfault. Fixing this by using pci_device_iommu_address_space()
> > instead to make sure address space were initialized at this time.
> >
> > With this fix, IOMMU device were required to be initialized before any
> > virtio-pci devices.
> >
> > Fixes: c611c76417f5 ("virtio: add MemoryListener to cache ring translations")
> > Cc: Paolo Bonzini <address@hidden>
> > Signed-off-by: Jason Wang <address@hidden>
> This is very ugly. I guess it's better than broken IOMMU ...
> Paolo?

Maybe we can delay the registering of memory listener on bus master 
enabling or status setting.

Thanks

> > ---
> >   hw/virtio/virtio-pci.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index 5ce42af..b76f3f6 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -1153,7 +1153,7 @@ static AddressSpace *virtio_pci_get_dma_as(DeviceState *d)
> >       VirtIOPCIProxy *proxy = VIRTIO_PCI(d);
> >       PCIDevice *dev = &proxy->pci_dev;
> >   
> > -    return pci_get_address_space(dev);
> > +    return pci_device_iommu_address_space(dev);
> >   }
> >   
> >   static int virtio_pci_add_mem_cap(VirtIOPCIProxy *proxy,
> > --
> > 2.7.4