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Re: [Qemu-devel] On block interface types in general, IF_AHCI in particu
From: |
Anthony Liguori |
Subject: |
Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular |
Date: |
Tue, 30 Oct 2012 14:03:08 -0500 |
User-agent: |
Notmuch/0.13.2+93~ged93d79 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) |
Kevin Wolf <address@hidden> writes:
> Am 30.10.2012 17:31, schrieb Paolo Bonzini:
>> Il 30/10/2012 15:43, Markus Armbruster ha scritto:
>>> There's a related argument that I find more compelling: we may want
>>> if=ahci to let users choose nicely between IDE and AHCI. Makes sense
>>> only if we have boards providing both kind of controllers onboard. q35
>>> doesn't.
>>
>> I think the main problem is that we haven't hashed out the requirements.
>> Since this is QEMU and not libvirt (which uses -drive if=none / -device
>> anyway), I suppose we mostly care about direct command-line start. We
>> want "qemu-kvm winxp.img" to work, even if q35 is now the default
>> machine. This calls for making IDE (not AHCI) the default.
>
> Yes. I think this is my main requirement: Command lines that work with
> 1.2 should usually keep working with whatever version introduces Q35 as
> the default.
>
>> The main drawback of if=ahci is, as pointed out by Markus, that you
>> would have to provide both controllers on-board. I think a real ICH9
>> has the compatibility IDE controller on a separate PCI address from the
>> SATA controller, so creating both of them is not really out of question.
>> Obvious disadvantage, it would depart from real hardware. Linux should
>> not care, not sure about SeaBIOS and Windows.
>
> Okay, so I guess the next step is finding out how real hardware works.
> Markus claims that there's no IDE mode on Q35 boards. I find this hard
> to believe and a quick search indeed suggests otherwise.
>
> What you're saying is that PCI addresses might be different for IDE and
> SATA mode, but on real hardware only one interface is exposed at the
> same time, right? This matches better what I remember, but we'd have to
> check the details.
>
>> At the same time, if all we want is a quick way to switch between IDE
>> and AHCI, we could just use machine types. So another proposal is to
>> have two machine types, one for ICH9-IDE (pc, the default), one for
>> ICH9-AHCI (q35), one for PIIX3-IDE (piix3). Each QEMU release would add
>> (up to) three machine types.
>
> I actually kind of like this solution.
A related option which I had previously suggested is a machine option of
"storage".
So you can do:
qemu --machine q35,storage=ide
qemu --machine i440fx,storage=scsi
qemu --machine i440fx,storage=virtio
etc.
I think it's rare that users want to have multiple storage types. They
probably this level of granularity.
Regards,
Anthony Liguori
>
> Kevin
- [Qemu-devel] On block interface types in general, IF_AHCI in particular, Markus Armbruster, 2012/10/30
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Jason Baron, 2012/10/30
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Paolo Bonzini, 2012/10/30
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Kevin Wolf, 2012/10/30
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular,
Anthony Liguori <=
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Anthony Liguori, 2012/10/30
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Markus Armbruster, 2012/10/31
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Peter Maydell, 2012/10/31
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Paolo Bonzini, 2012/10/31
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Markus Armbruster, 2012/10/31
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Paolo Bonzini, 2012/10/31
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Alexander Graf, 2012/10/31
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Paolo Bonzini, 2012/10/31
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Anthony Liguori, 2012/10/31
- Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular, Alexander Graf, 2012/10/31