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

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

[Jason Wang]

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>
---
 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

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

[Michael S. Tsirkin]

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?


> ---
>  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

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 <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

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

[Paolo Bonzini]

On 02/03/2017 08:47, Jason Wang wrote:
>>>
>>> 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.

Can we add a callback to PCIDeviceClass, and invoke it from
pci_init_bus_master?

Paolo

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

[Jason Wang]

On 2017年03月02日 18:30, Paolo Bonzini wrote:
>
> On 02/03/2017 08:47, Jason Wang wrote:
>>>> 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.
> Can we add a callback to PCIDeviceClass, and invoke it from
> pci_init_bus_master?
>
> Paolo
>

This looks pci specific, I post a fix that reset the dma_as during 
status set which can solve this issue too. Please have a look.

Thanks