Re: [Qemu-devel] issues of region cache and iommu reset

[Paolo Bonzini]

On 29/03/2017 10:37, Jason Wang wrote:
>>
>> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>> index 03592c5..73e69ac 100644
>> --- a/hw/virtio/virtio.c
>> +++ b/hw/virtio/virtio.c
>> @@ -176,6 +176,10 @@ err_used:
>>       address_space_cache_destroy(&new->desc);
>>   err_desc:
>>       g_free(new);
>> +    atomic_rcu_set(&vq->vring.caches, NULL);
>> +    if (old) {
>> +        call_rcu(old, virtio_free_region_cache, rcu);
>> +    }
>>   }
>>
>>   /* virt queue functions */
>>
>> Paolo
> 
> This looks a good fix but may not solve this issue completely. Depends
> on the iova that guest uses, address_space_cache_init() may succeed even
> in this case since vtd does a passthrough translation in this case.

Can you explain this more?

Paolo