Re: [Xen-devel] [RFC] Add support for Xen ARM guest on FreeBSD

[Warner Losh <imp@xxxxxxxxxx>]

On Jan 18, 2014, at 4:41 PM, Julien Grall wrote:

> 
> Hello Nathan,
> 
> On 01/17/2014 03:04 AM, Nathan Whitehorn wrote:
>> On 01/16/14 18:36, Julien Grall wrote:
>>> 
>>> 
>>> On 01/16/2014 01:56 AM, Nathan Whitehorn wrote:
>>> As I understand, only the simple bus code (see simplebus_attach) is
>>> translating the interrupts in the device on a resource.
>>> So if you have a node directly attached to the root node with
>>> interrupts and MMIO, the driver won't be able to retrieve and
>>> translate the interrupts via bus_alloc_resources.
> 
>> Why not? nexus on ARM, MIPS, PowerPC, and sparc64 can do this.
> 
> I have digged into the code to find the reason of my issue. FreeBSD is 
> receiving a VM fault when the driver (xen-dt) is trying to setup the IRQ.
> 
> This is because the GIC is not yet initialized but FreeBSD asks to unmask the 
> IRQ (sys/arm/arm/gic.c:306).
> 
> With this problem, all device nodes that are before the GIC in the device 
> tree can't have interrupts. For instance this simple device will segfault on 
> FreeBSD:
> 
> / {
> 
>  mybus {
>     compatible = "simple-bus";
> 
>     mynode {
>        interrupt-parent = &gic;
>        interrupts = <...>;
>     };
> 
>     gic: gic@xxxx {
>        interrupt-controller;
>     }
>  };
> };
> 
> The node "mynode" will have to move after the GIC to be able to work 
> correctly.

This stems from a difference in enumeration between FreeBSD and Linux. FreeBSD 
enumerates the devices in DTB order, while Linux does a partial ordering based 
on dependencies.

Warner
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