Re: [Qemu-devel] [PATCH v6 0/2] hw/arm: add 'virt' platform

[Alexander Graf]

On 13.08.2013, at 14:03, Peter Maydell wrote:

> This patch series adds a 'virt' platform which uses the
> kernel's mach-virt (fully device-tree driven) support
> to create a simple minimalist platform intended for
> use for KVM VM guests. It's based on John Rigby's
> patches, but I've overhauled it a lot:
> 
> * renamed user-facing machine to just "virt"
> * removed the A9 support (it can't work since the A9 has no
>   generic timers)
> * added virtio-mmio transports instead of random set of 'soc' devices
> * instead of updating io_base as we step through adding devices,
>   define a memory map with an array (similar to vexpress)
> * folded in some minor fixes from John's aarch64-support patch
> * rather than explicitly doing endian-swapping on FDT cells,
>   use fdt APIs that let us just pass in host-endian values
>   and let the fdt layer take care of the swapping
> * miscellaneous minor code cleanups and style fixes
> 
> If you want to test this with TCG QEMU you'll also need the
> generic-timers implementation patches I posted recently.
> A branch with generic-timers plus these patches is here:
> https://git.linaro.org/gitweb?p=people/pmaydell/qemu-arm.git;a=shortlog;h=refs/heads/mach-virt
> 
> (The kernel in pure mach-virt mode requires generic timers;
> it can't deal with getting its clock source from an sp804
> timer specified by the device tree. This might be fixed in
> a future kernel, but dropping all the soc-device support
> from mach-virt makes it simpler anyway.)
> 
> An obvious thing this machine does not provide is a serial
> port. I would rather just use virtio-console (and we
> should implement the 'emergency console/earlyprintk' bit of
> the virtio spec).

Are you sure about this? Not implementing a UART / something more standardized 
has been an absolute nightmare on s390. Device names diverge, so distributions 
get confused and there's this nasty bug somewhere in virtio-console that makes 
your input lag when you enter a lot of data quickly on the port.

I would really prefer to just define a UART for this machine. It will make life 
a lot easier.


Alex