On Thu, Nov 08, 2018 at 05:48:58PM +1100, Alexey Kardashevskiy wrote: > > > 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... Well, my point is the last paragraph of the commit message appears to be a rationale for this change in terms of what's needed for the GPU devices. But how those described properties of the GPU mean that region capabilites are useful / necessary isn't made clear. If it's not meant to be a rationale, I'm not sure what it's doing there at all. -- 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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