Re: [Qemu-devel] [RESEND RFC 0/6] AMD XGBE KVM platform passthrough

[Alex Williamson]

On Thu, 2015-11-19 at 15:22 +0000, Eric Auger wrote:
> I am resending this RFC from Oct 12, after kernel 4.4-rc1 and
> QEMU 2.5-rc1, hoping things have calmed down a little bit.
> 
> This RFC allows to set up AMD XGBE passthrough. This was tested on AMD
> Seattle.
> 
> The first upstreamed device supporting KVM platform passthrough was the
> Calxeda Midway XGMAC. Compared to this latter, the XGBE XGMAC exposes a
> much more complex device tree node. Generating the device tree node for
> the guest is the challenging and controversary part of this series.
> 
> - First There are 2 device tree node formats:
> one where XGBE and PHY are described in separate nodes and another one
> that combines both description in a single node (only supported by 4.2
> onwards kernels). Only the combined description is supported for passthrough,
> meaning the host must be >= 4.2 and must feature a device tree with a combined
> description. The guest will also be exposed with a combined description,
> meaning only >= 4.2 guest are supported. It is not planned to support
> separate node representation since assignment of the PHY is less
> straigtforward.
> 
> - the XGMAC/PHY node depends on 2 clock nodes (DMA and PTP).
> The code checks those clocks are fixed to make sure they cannot be
> switched off at some point after the native driver gets unbound.
> 
> - there are many property values to populate on guest side. Most of them
> cannot be hardcoded. That series proposes a way to parse the host device
> tree blob and retrieve host values to feed guest representation. Current
> approach relies on dtc binary availability plus libfdt usage.
> Other alternatives were discussed in:
> http://www.spinics.net/lists/kvm-arm/msg16648.html.
> 
> - Currently host booted with ACPI is not supported.

I won't pretend to know all the politics in the ARM space, but doesn't
this last bullet sort of imply that this is dead-on-arrival code?  Maybe
not in the embedded space, but certainly in the server space, I thought
ACPI was declared the winner.  Thanks,

Alex