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Re: [Qemu-ppc] [Qemu-devel] [PATCH 0/9] Add platform bus

From: Anthony Liguori
Subject: Re: [Qemu-ppc] [Qemu-devel] [PATCH 0/9] Add platform bus
Date: Mon, 22 Jul 2013 17:05:04 -0500
User-agent: Notmuch/0.15.2+202~g0c4b8aa (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu)

Peter Maydell <address@hidden> writes:

> On 22 July 2013 20:52, Anthony Liguori <address@hidden> wrote:
>> Alexander Graf <address@hidden> writes:
>>> On 22.07.2013, at 21:38, Anthony Liguori wrote:
>>> This could be used just the same for ARM's mach-virt, so I'd rather
>>> not make it e500 specific.
>> If someone designed a "virt" machine and didn't include PCI or some
>> other sane existing bus...
> "mach-virt" just means "completely described by device tree
> with no knowledge hardcoded in the kernel about the platform".

Fair enough.

> We don't currently have any PCI host controller which is:
> (a) for ARM

In QEMU?  You can make one super easily by just extending PCIHostState.

It's just a matter of mapping the index and data registers somewhere.

I can't believe it's that hard to get this working in Linux either.

> (b) entirely device tree driven

I'm not sure what this means, but presumably it wouldn't be hard to do
the above.

> (c) supported by QEMU

This part is easy enough.

> (d) with a decent Linux driver

See above.

> So mach-virt doesn't have PCI; it will use virtio-mmio,
> same as kvmtool for ARM does.

That's all well and fine but there are a lot of advantages to having PCI
and being able to use all of the features associated with it.

It's always tempting to reinvent the wheel when given the chance but I
think in the long term, you'll regret it.


Anthony Liguori

> -- PMM

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