Re: [9front] 9front on Xen 4.4 HVM

[mischief@9.offblast.org]

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I am the one who imported the xen kernel from labs and I ran 9front on xen a few months ago. It supports one cpu and iirc 512mb ram. I can recover my xen configs and post them shortly.

On February 21, 2015 10:46:12 AM PST, Giacomo Tesio <giacomo@tesio.it> wrote:
>Thanks for your help cinap.  It's an interesting dive into the kernel
>internals.
>
>Btw, I've tried various combinations of networks drivers (virtio-net
>or rtl) and plan9.ini options but with no success.
>
>Now I'm planning to write a plan9.ini menu with the following
>configurations trying one after another looking for a working
>solution.
>
>As far as I have undestood, I should test
>1) *npmp=
>2) *nomsi=
>3) *acpi=
>and the 4 combinations of them, right?
>
>Is there anything else that I can do to identify and fix the issue?
>
>I assigned to the 9front guest only one cpu, to reduce the variables,
>but actually, if to run on xen 9front must use a single cpu, then the
>disadvantage of the pv guest will be lower, and I could give it a try
>too.
>
>Strangely, looks like I'm the first to try installing plan9 on xen in
>the last few years...
>
>
>Giacomo
>
>2015-02-21 12:51 GMT+01:00  <cinap_lenrek@felloff.net>:
>> well, that sounds like a interrupt problem indeed. when you send
>> packets, all the driver does is to put packets in transmit ring
>> and optionally kick the card with some register that it should start
>> transmitting.
>>
>> but receiving works by the card issuing a interrupt and then the
>> driver looks in the receive ring if there are new packets from the
>> card.
>>
>> if interrupt couldnt be enabled (because if broken mp tables), then
>> we wont receive anything. but sending might still work because it
>> doesnt need an interrupt.
>>
>> the relation with mp is that mp systems use the apic interrupt
>> controller instead of the legacy pic controller (it is mandatory
>> as you need to use the apic to bootstrap the other processors).
>>
>> enabling interrupt on pic is easy. you read the irq register
>> from the pci config space (that the bios programmed for you)...
>> sometimes, pci interrupt router needs to be programmed.
>>
>> apic is a bit more complicated than pic because there can be multiple
>> apic controllers (and multiple processors/lapic's) and we require
>> tables (from bios) to find the mapping from pci bus interrupt
>> lines to the apics (which can then be programmed to send interrupts
>> to the lapics/processors).
>>
>> and then theres msi interrupts that *some* devices support that
>> do not require any tables. you program register in pci config
>> space for the device and you'r done. this also works only with
>> apic.
>>
>> when you specify *acpi= in plan9.ini, then the kernel will use
>> the acpi tables instead of the mp tables.
>>
>> when you use *nomp=, then we will use legacy pic interrupt controller
>> and only one cpu can be used (this is also what happens when we
>cannot
>> find mp table).
>>
>> --
>> cinap

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