Re: [PATCH kernel RFC 0/3] powerpc/pseries/iommu: GPU coherent memory pass through

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 25/07/2018 19:50, Alexey Kardashevskiy wrote:
> I am trying to pass through a 3D controller:
> [0302]: NVIDIA Corporation GV100GL [Tesla V100 SXM2] [10de:1db1] (rev a1)
> 
> which has a quite unique feature as coherent memory directly accessible
> from a POWER9 CPU via an NVLink2 transport.
> 
> So in addition to passing a PCI device + accompanying NPU devices,
> we will also be passing the host physical address range as it is done
> on the bare metal system.
> 
> The memory on the host is presented as:
> 
> ===
> [aik@yc02goos ~]$ lsprop /proc/device-tree/memory@42000000000
> ibm,chip-id      000000fe (254)
> device_type      "memory"
> compatible       "ibm,coherent-device-memory"
> reg              00000420 00000000 00000020 00000000
> linux,usable-memory
>                  00000420 00000000 00000000 00000000
> phandle          00000726 (1830)
> name             "memory"
> ibm,associativity
>                  00000004 000000fe 000000fe 000000fe 000000fe
> ===
> 
> and the host does not touch it as the second 64bit value of
> "linux,usable-memory" - the size - is null. Later on the NVIDIA driver
> trains the NVLink2 and probes this memory and this is how it becomes
> onlined.
> 
> In the virtual environment I am planning on doing the same thing,
> however there is a difference in 64bit DMA handling. The powernv
> platform uses a PHB3 bypass mode and that just works but
> the pseries platform uses DDW RTAS API to achieve the same
> result and the problem with this is that we need a huge DMA
> window to start from zero (because this GPU supports less than
> 50bits for DMA address space) and cover not just present memory
> but also this new coherent memory.
> 
> 
> This is based on sha1
> d72e90f3 Linus Torvalds "Linux 4.18-rc6".
> 
> Please comment. Thanks.


Ping?


> 
> 
> 
> Alexey Kardashevskiy (3):
>   powerpc/pseries/iommu: Allow dynamic window to start from zero
>   powerpc/pseries/iommu: Force default DMA window removal
>   powerpc/pseries/iommu: Use memory@ nodes in max RAM address
>     calculation
> 
>  arch/powerpc/platforms/pseries/iommu.c | 77 ++++++++++++++++++++++++++++++----
>  1 file changed, 70 insertions(+), 7 deletions(-)
> 

-- 
Alexey