Re: [meta-virtualization] Loading the module xen-gntdev on boot

[Paulo Sherring <pauloasherring@gmail.com>]

Hi Bertrand,
One very important piece of information I missed to disclose: I am not
using runqemu,
as it was not being properly set by the resulting bitbake build (the
resulting image was
pointing to the kernel instead of the xen binary).

So, I am launching it "by hand":

./tmp/work/x86_64-linux/qemu-helper-native/1.0-r1/recipe-sysroot-native/usr/bin/qemu-system-aarch64
\
-nographic  \
-machine virt,gic-version=3 \
-machine virtualization=true \
-cpu cortex-a57 -smp 4 -m 4G -machine type=virt \
-bios ./tmp/deploy/images/qemuarm64/u-boot-qemuarm64.bin \
-device loader,file=./tmp/deploy/images/qemuarm64/xen-qemuarm64,addr=0x45000000
\
-device loader,file=./tmp/deploy/images/qemuarm64/Image--5.10.103+git0+792f1272dd_3aab5bb12b-r0-qemuarm64-20220317212819.bin,addr=0x46000000
\
-device loader,file=./tmp/deploy/images/qemuarm64/Image--5.10.103+git0+792f1272dd_3aab5bb12b-r0-qemuarm64-20220317212819.bin,addr=0x48000000
\
-device loader,file=./virt.dtb,addr=0x44000000 \
-drive id=disk0,file=./tmp/deploy/images/qemuarm64/xen-image-minimal-qemuarm64.ext4,if=none,index=0,format=raw
\
-device virtio-blk-device,drive=disk0 \

And then stop it on u-boot, and setup the fdt:
## Dom0 only:
fdt addr 0x44000000
fdt resize
fdt set /chosen \#address-cells <1>
fdt set /chosen \#size-cells <1>
fdt set /chosen xen,xen-bootargs "dom0_mem=512M"
fdt mknod /chosen module@0
fdt set /chosen/module@0 compatible "xen,linux-zimage" "xen,multiboot-module"
fdt set /chosen/module@0 reg <0x46000000 0x1373a00>
fdt set /chosen/module@0 bootargs "dom0_mem=512M root=/dev/vda rw
earlyprintk=serial,ttyAMA0 console=ttyAMA0,115200n8 earlycon=xenboot"
booti 0x45000000 - 0x44000000

Please find also some more information below:

On Tue, Mar 22, 2022 at 12:59 PM Bertrand Marquis
<Bertrand.Marquis@arm.com> wrote:
>
> Hi Paulo,
>
> Hardknott is long term while honister is not but both are stable releases.
>
> I am not quite sure I get your 4.14 pulling 4.16. The 4.14 recipe is building the latest 4.14 version of Xen.
>
That was just me being silly. I was looking into xen_git.bb which
clearly is not the preferred provider. I am in fact using Xen 4.14, as
you pointed out. Sorry for the mistake.
> From what I see modules to load are in a xen.conf in modules-load.d generated by Xen tools compilation.
> Gntdev is properly listed in the current xen source tree as one of the default modules to actually load on boot.
>
> Can you check the content of modules-load.d/xen.conf (somewhere in /etc in your dom0 roots) ?
>
I have nothing there. But, I did have two hits when searching the rootfs:
/etc/tmpfiles.d/xen.conf
/lib/systemd/modules-load.d/xen.conf
Not sure if there there is some sort of startup script that was
supposed to move around these files
or even if systemd-modules-load.service would be supposed to be
looking elsewhere.

> It could be that this was actually missing in the xen release you are building or that systemd is not actually loading modules listed there.
>
> Cheers
> Bertrand
Cheers, Paulo.

____

> > On 22 Mar 2022, at 13:38, Paulo Sherring <pauloasherring@gmail.com> wrote:
> >
> > Hello Bertrand,
> >
> > On Tue, Mar 22, 2022 at 12:28 PM Bertrand Marquis
> > <Bertrand.Marquis@arm.com> wrote:
> >>
> >> Hi Paulo,
> >>
> >> Please always keep the mailing list in as me asking the questions does not mean I will necessarily be the one working on this.
> >>
> > Oops, my mistake, sorry.
> >
> >> Please see some questions here after.
> >>
> >>> On 22 Mar 2022, at 12:03, Paulo Sherring <pauloasherring@gmail.com> wrote:
> >>>
> >>> Hello Bertrand,
> >>>
> >>> On Tue, Mar 22, 2022 at 10:44 AM Bertrand Marquis
> >>> <Bertrand.Marquis@arm.com> wrote:
> >>>>
> >>>> Hi Paulo,
> >>>>
> >>>>> On 22 Mar 2022, at 11:33, Paulo Sherring via lists.yoctoproject.org <pauloasherring=gmail.com@lists.yoctoproject.org> wrote:
> >>>>>
> >>>>> Hello all,
> >>>>> I am a bit new to meta-virtualization and to the Xen project And to
> >>>>> virtualizations, so please bear with me :)
> >>>>> I've been trying to make use of the xen project, currently targeting
> >>>>> qemu (and later on, rpi4). After messing around, I was able to boot
> >>>>> dom0 and a domU.
> >>>>> But, I had to add the xen-gntdev to the `modules-load.d,` because
> >>>>> `xenstored` was failing to start, due to some missing connection,
> >>>>> probably brought up by xen-gntdev module.
> >>>>>
> >>>>> As I am new to all this, I was just wondering if this is by design, or
> >>>>> this is an issue (and therefore, I should/could submit a patch).
> >>>>
> >>>> No problem at all and thanks a lot for the feedback.
> >>>> This should not happen and should be fixed.
> >>>>
> >>>> Could you tell us what you are building (which image) and what parameters did you set in your local.conf ?
> >>>>
> >>>
> >>> - Baseline is hardknott.
> >>
> >> Any reason not to use honester ?
> >>
> > The main reason was that hardknott is tagged as a stable release and
> > it already includes xen 4.14 or latest (it is actually pulling 4.16),
> > which I wanted/will need for RPi4 support.
>
>