[fedora-arm] Debugging our kernels under qemu + gdb

[Michael Hope]

On 14 May 2012 16:57, Jon Masters <jcm at redhat.com> wrote:
> On 05/13/2012 04:34 PM, Michael Hope wrote:
>> On 12 May 2012 22:12, Richard W.M. Jones <rjones at redhat.com> wrote:
>>> On Fri, May 11, 2012 at 01:41:43PM -0700, Brendan Conoboy wrote:
>>>> On 05/11/2012 01:04 PM, Richard W.M. Jones wrote:
>>>>> Has anyone tried to debug our Fedora/arm kernels under qemu-system-arm?
>>>>> (In this case, the host is also arm, but I don't think that matters.)
>>>>
>>>> Richard,
>>>>
>>>> FYI, we as of a few hours ago have nearly-official F17-beta images
>>>> for versatile express on the following page:
>>>>
>>>> http://scotland.proximity.on.ca/arm-nightlies/
>>>>
>>>> There's a link for vexpress and vexpress+x rootfs images.  A second
>>>> link provides a kernel, initramfs, and script for starting qemu.
>>>> Note that vexpress is much faster than versatile and allows more ram
>>>> (1GB). Recommend you try this out!
>>>
>>> So one issue appears to be lack of PCI support (according to Linaro's
>>> notes: https://wiki.linaro.org/PeterMaydell/QemuVersatileExpress).
>>>
>>> Unfortunately all of the virtio hardware is PCI-based, so it doesn't
>>> seem like this is going to work for the virt tools :-(
>>
>> Hi Richard.  The plan is to use virtio-mmio and use Device Tree to set
>> where the virtio devices are.  virtio-mmio is in the mainline kernel
>> and in the queue for QEMU.
>
> Note, we're not using dtb (device tree) yet in the qemu kernel. To do
> that properly, we'll need to get a qemu that works with U-Boot, etc. I
> know Linaro have put such a combination together, right? Should any of
> that be working with upstream bits yet? Brendan mentioned he'd tried
> poking briefly at the U-Boot that Linaro put together but it apparently
> didn't boot on our qemu (I know upstream was missing e.g. the model
> instantiation for the hardware memory controller, etc. in vexpress).
>
> I guess I could/should ping Peter Maydell? Is he the best contact?

Peter or Ricardo, yip.  Ricardo has a good handle on the integration
work that's been done and the upstream versions.

We've standardised on the vexpress-a9 model as it's neutral, has a
good amount of RAM,  and has good support in upstream QEMU and
mainline Linux.  The vexpress-a15 isn't as tested but goes up to 2 GB
and will probably be the base model for KVM.

-- Michael