Re: PvGRUB2 on Arm64?

[Juergen Gross <jgross@xxxxxxxx>]

On 07.10.22 12:13, Benjamin Mordaunt wrote:
> Yes in effect, that is what I want.
>
> There seems to be a GRUB2 module which works in the opposite direction
> (https://github.com/rhboot/grub2/blob/fedora-38/grub-core/loader/arm64/xen_boot.c 
> <https://github.com/rhboot/grub2/blob/fedora-38/grub-core/loader/arm64/xen_boot.c>),
> which allows launching the Xen hypervisor from GRUB, but I want to launch GRUB2
> with PV drivers as the bootloader for a DomU (Ubuntu in my case). Looks like we 
> need
> an equivalent arm64 relocator.S as provided for x86 in
> https://github.com/rhboot/grub2/blob/fedora-38/grub-core/lib/x86_64/xen/relocator.S 
> <https://github.com/rhboot/grub2/blob/fedora-38/grub-core/lib/x86_64/xen/relocator.S>.
No, this is really for guests running in PV mode (this is a x86-only special
variant for guests not needing any hardware virtualization support).

PV device support is completely unrelated to that.

This is why I mentioned the i386-xen_pvh variant of grub, as the x86 PVH
guests are very similar to the Xen guests on Arm[64].


Juergen

> Ben
>
> On Fri, Oct 7, 2022 at 10:51 AM Juergen Gross <jgross@xxxxxxxx 
> <mailto:jgross@xxxxxxxx>> wrote:
>     On 07.10.22 11:04, Benjamin Mordaunt wrote:
>      > Hi,
>      >
>      > Pygrub is insufficient for my use case (it also seems to have quite a
>     major bug
>      > traversing GPT partition tables – in my case it identifies 128 partitions
>     all at
>      > offset 0 for a 2-partition image), therefore I wish to use 
> paravirtualized
>      > GRUB2. However, it doesn’t seem as though Xen is a supported platform for
>      > PvGRUB2 like it is for x86_64 and i386. Is this really the case? Is there
>     a way
>      > I can use PvGRUB2 on Arm64? If not, is there investigation/development
>     ongoing?
>
>     So you are basically looking for grub2 with Xen PV drivers.
>
>     That should be doable, but it requires at least some work. The best way 
> forward
>     would be to have grub2 modules for that purpose.
>
>     The code is there already, it "only" needs to be made generally available 
> and
>     be activated. A good blueprint for that is the i386-xen_pvh variant of 
> grub2.
>
>     Unfortunately I don't have time now to work on that.
>
>
>     Juergen

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