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Re: [Qemu-devel] [PATCH 2/3] ppc64-softmmu: Remove unsupported FDC from

From: Alexander Graf
Subject: Re: [Qemu-devel] [PATCH 2/3] ppc64-softmmu: Remove unsupported FDC from config
Date: Wed, 11 Mar 2015 06:27:56 -0500
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.5.0

On 10.03.15 04:20, Alexey Kardashevskiy wrote:
> On 03/10/2015 04:38 PM, Alexander Graf wrote:
>>> Am 09.03.2015 um 23:44 schrieb Alexey Kardashevskiy <address@hidden>:
>>>> On 03/10/2015 02:58 PM, David Gibson wrote:
>>>>> On Tue, Mar 10, 2015 at 02:52:48PM +1100, Alexey Kardashevskiy wrote:
>>>>>> On 03/10/2015 01:39 AM, Alexey Kardashevskiy wrote:
>>>>>>> On 03/09/2015 11:31 PM, Alexander Graf wrote:
>>>>>>>> On 02.03.15 00:46, Alexey Kardashevskiy wrote:
>>>>>>>> This removes floppy disks support as it is not supported by any
>>>>>>>> PPC64
>>>>>>>> system anyway as the only way to have floppy disk on such
>>>>>>>> systems would
>>>>>>>> be an ISA bus and Linux kernels seems have never had such support.
>>>>>>>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
>>>>>>> I removed this patch from my queue again. The ppc64-softmmu
>>>>>>> target can
>>>>>>> execute -M PReP which in turn uses the fdc.
>>>>>> Out of curiosity - do you have actual 64bit guests being able to
>>>>>> run on
>>>>>> PReP? :) Current Linux ditched its support...
>>>>> Paul suggested that there has never ever been a 64bit PReP CPU so
>>>>> there is
>>>>> no point in emulating it in QEMU. Or there is some reason for that?
>>>> IIUC, qemu-system-ppc64 (roughly speaking) emulates a superset of what
>>>> qemu-system-ppc does, not a different set of hardware.
>>> Well, default-configs/ppc-softmmu.mak does not include
>>> default-configs/ppc64-softmmu.mak or vice versa so I would say these
>>> are pretty independent and I would simply remove CONFIG_PREP* from
>>> default-configs/ppc64-softmmu.mak.
>> Convention so far has been that ppc64 includes ppc includes ppcemb. I
>> don't see why we should break that assumption.
> address@hidden ~]$ ./qemu-system-ppc64 -device help 2>&1 | grep fdc
> name "isa-fdc", bus ISA
> name "sysbus-fdc", bus System
> afaik there is no way to get "fdc" working with qemu-system-ppc64 but

It might work with -M prep, but definitely not any of the others. The
same holds true for qemu-system-ppc. There also only -M prep supports an
ISA bus, all the other machines don't.

> "-device help" suggests there is a way and libvirt thinks (the original
> request came from there) it can add floppy disk. If later we use "-fda"
> with QEMU, it will warn about "Orphaned drive" as there is no fdc
> device. Ok, I can be sneakier and add "-device i82378" but I wonder if
> there is a PPC64 guest with FDC driver enabled. When I try to enable it
> in the current upstream (or anything since 2010), it needs ISA which
> depends on CHRP (about to be ditched, and PReP is ditched already) which
> depends on 6xx which is not defined at all (PPC_6xx is but not 6xx).

The fact that we have an fdc in the "device bucket" doesn't mean that
that particular device can ever be instantiated. We don't have an ISA
bus, so we can't really ;).

> So if you know how to get working floppy disk with qemu-system-ppc64,
> that would help me a lot in rejecting requests from libvirt folks :)
> Thanks :)

I don't think you want floppy disk emulation on -M pseries at all. In
fact, you only ever want floppy disk emulation on x86. So I'd recommend
to change the logic in libvirt accordingly and just hard code floppy
emulation to x86 (and if alpha or some other weird architecture needs it
later as well, have them extend the list).


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