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

[Alexey Kardashevskiy]

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.


> 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 <address@hidden>
>> ---
>> 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