Date: Sat, 18 Jan 2014 19:44:09 -0700 From: Warner Losh <imp@bsdimp.com> To: Julien Grall <julien.grall@linaro.org> Cc: ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, xen-devel@lists.xen.org, freebsd-xen@freebsd.org, freebsd-arm@FreeBSD.org, Nathan Whitehorn <nwhitehorn@freebsd.org>, gibbs@freebsd.org Subject: Re: [RFC] Add support for Xen ARM guest on FreeBSD Message-ID: <3AE8EDE6-D931-4F93-9BF7-ABFB297B5B96@bsdimp.com> In-Reply-To: <52DB1138.6010804@linaro.org> References: <1389733267-20822-1-git-send-email-julien.grall@linaro.org> <24851B79-7EC7-4E3A-94DB-4B9B86FDFFFC@bsdimp.com> <52D6B62A.9000208@linaro.org> <52D73C4E.2080306@freebsd.org> <52D87B15.5090208@linaro.org> <52D89DC9.7050303@freebsd.org> <52DB1138.6010804@linaro.org>
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On Jan 18, 2014, at 4:41 PM, Julien Grall wrote:
>=20
> Hello Nathan,
>=20
> On 01/17/2014 03:04 AM, Nathan Whitehorn wrote:
>> On 01/16/14 18:36, Julien Grall wrote:
>>>=20
>>>=20
>>> 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.
>=20
>> Why not? nexus on ARM, MIPS, PowerPC, and sparc64 can do this.
>=20
> 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.
>=20
> This is because the GIC is not yet initialized but FreeBSD asks to =
unmask the IRQ (sys/arm/arm/gic.c:306).
>=20
> 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:
>=20
> / {
>=20
> mybus {
> compatible =3D "simple-bus";
>=20
> mynode {
> interrupt-parent =3D &gic;
> interrupts =3D <...>;
> };
>=20
> gic: gic@xxxx {
> interrupt-controller;
> }
> };
> };
>=20
> 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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