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

David Gibson
2018-11-08T06:21:39Z

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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.

>
> 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;
> + }
> }
> }
>

--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson

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