Re: [Adeos-main] Reworking ipipe timer subsystem,

[Jan Kiszka <jan.kiszka@domain.hid>]

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On 2012-04-03 09:54, Gilles Chanteperdrix wrote:
> On 04/02/2012 11:58 PM, Jan Kiszka wrote:
>> On 2012-04-02 23:55, Gilles Chanteperdrix wrote:
>>> On 04/02/2012 10:59 PM, Jan Kiszka wrote:
>>>> On 2012-04-02 22:56, Jan Kiszka wrote:
>>>>>> No luck, I am using qemu 0.12.5, there is no -global option documented,
>>>>>
>>>>> Err, that's prehistoric. Use stable 1.0.x at least to receive proper
>>>>> HPET support.
>>>>
>>>> Oh, and there is one further pitfall: You need to provide
>>>> -no-kvm-irqchip to use the HPET with MSI support because qemu-kvm does
>>>> not forward those MSIs to the kernel irqchip model. I'm sitting on
>>>> patches...
>>>
>>> Yes, I needed that. It works now, except that I could not find how to
>>> use an NFS root filesystem. But with an ext3 file-backed filesystem, I
>>> could get that:
>>
>> If your NFS server runs on the host and you use userspace networking
>> (default without additional parameters), the guest should be able to
>> reach the server under 10.0.2.2 and use an IP like 10.0.2.15 (or dhcp).
>> However, I recently failed to get this working as well but didn't dig
>> deeper.
> 
> Well, with -net user, I do not get any network interface on the
> simulated kernel. Maybe there a special network driver to enable in the
> kernel? The documentation does not say which network card is simulated,
> and I do not see any with lspci.

qemu-kvm emulates a rtl8139 by default. But, by just specifying -net
user, you disable any network adapter. Just leave it out, -net user -net
nic,model=rtl8139 is default.

> 
> Something else, is it possible to run kvm using SCHED_FIFO policy? I
> tried that and I almost got a lockup, was probably saved by throttling.

Yes, but not without some patches and a lot of tuning on both guest and
host side. A standard Linux kernel touches too many device models that
will take a long time to make RT compatible. A simple access to a
virtual graphic adapter will be like accessing a screwed up physical GPU
with horrible latency.

Jan


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