Re: [PATCH kernel 2/3] vfio_pci: Allow regions to add own capabilities

[Alexey Kardashevskiy <aik@ozlabs.ru>]

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On 08/11/2018 17:21, David Gibson wrote:
> On Mon, Oct 15, 2018 at 08:42:32PM +1100, Alexey Kardashevskiy wrote:
>> VFIO regions already support region capabilities with a limited set of
>> fields. However the subdriver might have to report to the userspace
>> additional bits.
>>
>> This adds an add_capability() hook to vfio_pci_regops.
>>
>> This is aiming Witherspoon POWER9 machines which have multiple
>> interconnected NVIDIA V100 GPUs with coherent RAM; each GPU's RAM
>> is mapped to a system bus and to each of GPU internal system bus and
>> the GPUs use this for DMA routing as DMA trafic can go via any
>> of many NVLink2 (GPU-GPU or GPU-CPU) or even stay local within a
>> GPU.
> 
> This description doesn't really make clear how per-region capabilities
> are relevant to these devices.


I am confused. This patch just adds a hook, and the device specifics are
explained in the next patch where they are used...


> 
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> ---
>>
>> This is based on top of "vfio_pci: Allow mapping extra regions"
>> ---
>>  drivers/vfio/pci/vfio_pci_private.h | 3 +++
>>  drivers/vfio/pci/vfio_pci.c         | 6 ++++++
>>  2 files changed, 9 insertions(+)
>>
>> diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
>> index 86aab05..93c1738 100644
>> --- a/drivers/vfio/pci/vfio_pci_private.h
>> +++ b/drivers/vfio/pci/vfio_pci_private.h
>> @@ -62,6 +62,9 @@ struct vfio_pci_regops {
>>  	int	(*mmap)(struct vfio_pci_device *vdev,
>>  			struct vfio_pci_region *region,
>>  			struct vm_area_struct *vma);
>> +	int	(*add_capability)(struct vfio_pci_device *vdev,
>> +				  struct vfio_pci_region *region,
>> +				  struct vfio_info_cap *caps);
>>  };
>>  
>>  struct vfio_pci_region {
>> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
>> index 7923314..4a3b93e 100644
>> --- a/drivers/vfio/pci/vfio_pci.c
>> +++ b/drivers/vfio/pci/vfio_pci.c
>> @@ -759,6 +759,12 @@ static long vfio_pci_ioctl(void *device_data,
>>  			if (ret)
>>  				return ret;
>>  
>> +			if (vdev->region[i].ops->add_capability) {
>> +				ret = vdev->region[i].ops->add_capability(vdev,
>> +						&vdev->region[i], &caps);
>> +				if (ret)
>> +					return ret;
>> +			}
>>  		}
>>  		}
>>  
> 

-- 
Alexey


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