[libvirt] [PATCH v5 1/2] qemu_domain: NVLink2 bridge detection function for PPC64

[Erik Skultety]

On Thu, Apr 04, 2019 at 10:40:38AM -0300, Daniel Henrique Barboza wrote:
> The NVLink2 support in QEMU implements the detection of NVLink2
> capable devices by verifying the attributes of the VFIO mem region
> QEMU allocates for the NVIDIA GPUs. To properly allocate an
> adequate amount of memLock, Libvirt needs this information before
> a QEMU instance is even created, thus querying QEMU is not
> possible and opening a VFIO window is too much.
>
> An alternative is presented in this patch. Making the following
> assumptions:
>
> - if we want GPU RAM to be available in the guest, an NVLink2 bridge
> must be passed through;
>
> - an unknown PCI device can be classified as a NVLink2 bridge
> if its device tree node has 'ibm,gpu', 'ibm,nvlink',
> 'ibm,nvlink-speed' and 'memory-region'.
>
> This patch introduces a helper called @ppc64VFIODeviceIsNV2Bridge
> that checks the device tree node of a given PCI device and
> check if it meets the criteria to be a NVLink2 bridge. This
> new function will be used in a follow-up patch that, using the
> first assumption, will set up the rlimits of the guest
> accordingly.
>
> Signed-off-by: Daniel Henrique Barboza <danielhb413 at gmail.com>
> ---
Reviewed-by: Erik Skultety <eskultet at redhat.com>