Re: [Qemu-devel] [PATCH v8 4/4] vfio: Enable for SPAPR

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 06/07/2014 08:47 AM, Alexey Kardashevskiy wrote:
> On 06/07/2014 02:57 AM, Alex Williamson wrote:
>> On Fri, 2014-06-06 at 13:34 +1000, Alexey Kardashevskiy wrote:
>>> This turns the sPAPR support on and enables VFIO container use
>>> in the kernel.
>>>
>>> This extends vfio_connect_container to support VFIO_SPAPR_TCE_IOMMU type
>>> in the host kernel.
>>>
>>> This registers a memory listener which sPAPR IOMMU will notify when
>>> executing H_PUT_TCE/etc DMA calls. The listener then will notify the host
>>> kernel about DMA map/unmap operation via VFIO_IOMMU_MAP_DMA/
>>> VFIO_IOMMU_UNMAP_DMA ioctls.
>>>
>>> This executes VFIO_IOMMU_ENABLE ioctl to make sure that the IOMMU is free
>>> of mappings and can be exclusively given to the user. At the moment SPAPR
>>> is the only platform requiring this call to be implemented.
>>>
>>> Note that the host kernel function implementing VFIO_IOMMU_DISABLE
>>> is called automatically when container's fd is closed so there is
>>> no need to call it explicitly from QEMU. This may change in the future.
>>
>> So you're saying we rely on a behavior that may change in the future...
>> The kernel must do cleanup, it can never rely on userspace to do the
>> right thing or we have a bug.  Does that mean we can remove the "may
>> change in the future" part of this comment or is that directed at QEMU's
>> behavior and not the kernel's? 
> 
> 
> I wanted to say that if/when we support PCI hotplug or dynamic IOMMU group
> reconfiguration (we might be able to do so in POWER9 or later, do not know
> details), we will call DISABLE explicitly.


Any better?
===
    Note that the host kernel function implementing VFIO_IOMMU_DISABLE
    is called automatically when container's fd is closed so there is
    no need to call it explicitly from QEMU. We may need to call
    VFIO_IOMMU_DISABLE explicitely in the future for some sort of dynamic
    reconfiguration (PCI hotplug or dynamic IOMMU group management).
===

Thanks!

> 
> 
>> A comment in the code where we setup the
>> release handler or call ENABLE would be a good idea too.  Thanks,
> 
> 
> 
> 
>>
>> Alex
>>
>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>> ---
>>> Changes:
>>> v8:
>>> * added note about VFIO_IOMMU_DISABLE in the commit log
>>>
>>> v7:
>>> * added more details in commit log
>>>
>>> v5:
>>> * multiple returns converted to gotos
>>>
>>> v4:
>>> * fixed format string to use %m which is a glibc extension:
>>> "Print output of strerror(errno). No argument is required."
>>> ---
>>>  hw/misc/vfio.c | 28 ++++++++++++++++++++++++++++
>>>  1 file changed, 28 insertions(+)
>>>
>>> diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
>>> index bb77934..78d2045 100644
>>> --- a/hw/misc/vfio.c
>>> +++ b/hw/misc/vfio.c
>>> @@ -3650,6 +3650,34 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
>>>  
>>>          container->iommu_data.type1.initialized = true;
>>>  
>>> +    } else if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_IOMMU)) {
>>> +        ret = ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &fd);
>>> +        if (ret) {
>>> +            error_report("vfio: failed to set group container: %m");
>>> +            ret = -errno;
>>> +            goto free_container_exit;
>>> +        }
>>> +
>>> +        ret = ioctl(fd, VFIO_SET_IOMMU, VFIO_SPAPR_TCE_IOMMU);
>>> +        if (ret) {
>>> +            error_report("vfio: failed to set iommu for container: %m");
>>> +            ret = -errno;
>>> +            goto free_container_exit;
>>> +        }
>>> +
>>> +        ret = ioctl(fd, VFIO_IOMMU_ENABLE);
>>> +        if (ret) {
>>> +            error_report("vfio: failed to enable container: %m");
>>> +            ret = -errno;
>>> +            goto free_container_exit;
>>> +        }
>>> +
>>> +        container->iommu_data.type1.listener = vfio_memory_listener;
>>> +        container->iommu_data.release = vfio_listener_release;
>>> +
>>> +        memory_listener_register(&container->iommu_data.type1.listener,
>>> +                                 container->space->as);
>>> +
>>>      } else {
>>>          error_report("vfio: No available IOMMU models");
>>>          ret = -EINVAL;
>>
>>
>>
> 
> 


-- 
Alexey