Am 30.10.2015 um 13:17 schrieb Cornelia Huck:
> On Tue, 27 Oct 2015 23:48:51 +0100
> Christian Borntraeger <borntrae...@de.ibm.com> wrote:
> 
>> With all infrastructure in place, lets provide dma_ops for virtio
>> devices on s390.
>>
>> Signed-off-by: Christian Borntraeger <borntrae...@de.ibm.com>
>> ---
>>  drivers/s390/virtio/kvm_virtio.c | 2 ++
>>  drivers/s390/virtio/virtio_ccw.c | 2 ++
>>  2 files changed, 4 insertions(+)
>>
>> diff --git a/drivers/s390/virtio/kvm_virtio.c 
>> b/drivers/s390/virtio/kvm_virtio.c
>> index 53fb975..05adaa9 100644
>> --- a/drivers/s390/virtio/kvm_virtio.c
>> +++ b/drivers/s390/virtio/kvm_virtio.c
>> @@ -13,6 +13,7 @@
>>  #include <linux/kernel_stat.h>
>>  #include <linux/init.h>
>>  #include <linux/bootmem.h>
>> +#include <linux/dma-mapping.h>
>>  #include <linux/err.h>
>>  #include <linux/virtio.h>
>>  #include <linux/virtio_config.h>
>> @@ -318,6 +319,7 @@ static void add_kvm_device(struct kvm_device_desc *d, 
>> unsigned int offset)
>>              return;
>>      }
>>
>> +    kdev->vdev.dev.archdata.dma_ops = &dma_noop_ops;
> 
> This provides dma_ops for the vdev, while Andy's virtio code looks for
> dma_ops in the vdev's parent (in the ccw and pci cases, the proxy
> device; in this case, it would be our root device).
> 
> With
> 
> diff --git a/drivers/s390/virtio/kvm_virtio.c 
> b/drivers/s390/virtio/kvm_virtio.c
> index 05adaa9..5f79c52 100644
> --- a/drivers/s390/virtio/kvm_virtio.c
> +++ b/drivers/s390/virtio/kvm_virtio.c
> @@ -319,7 +319,6 @@ static void add_kvm_device(struct kvm_device_desc *d, 
> unsigned int offset)
>               return;
>       }
> 
> -     kdev->vdev.dev.archdata.dma_ops = &dma_noop_ops;
>       kdev->vdev.dev.parent = kvm_root;
>       kdev->vdev.id.device = d->type;
>       kdev->vdev.config = &kvm_vq_configspace_ops;
> @@ -473,6 +472,7 @@ static int __init kvm_devices_init(void)
>               vmem_remove_mapping(total_memory_size, PAGE_SIZE);
>               return rc;
>       }
> +     kvm_root->archdata.dma_ops = &dma_noop_ops;
> 
>       INIT_WORK(&hotplug_work, hotplug_devices);
> 
> applied (and the endianness fix in the virtio code), I can boot a
> s390-virtio guest as well.

I am currently reworking this to 

 static inline struct dma_map_ops *get_dma_ops(struct device *dev)
 {
        if (dev && dev->archdata.dma_ops)
                return dev->archdata.dma_ops;
        return &dma_noop_ops;
 }


Which uses the dma_noop_ops for everything unless the device overrides (PCI 
does)

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