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

[Jason Wang <jasowang@redhat.com>]

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 <pbonzini@redhat.com>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
> 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