Re: [Xen-devel] [PATCH] Improve Dom0-less documentation

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 7/9/19 8:23 AM, Viktor Mitin wrote:
> On Mon, Jul 8, 2019 at 6:45 PM Julien Grall <julien.grall@xxxxxxx> wrote:
> > Hello,
> Hello Julien,
>
> > On 7/8/19 1:35 PM, Viktor Mitin wrote:
> > > Updated configuration example according to arm64
> > > and added more cases about known xl limitations.
> > dom0less is not an arm64 specific feature. It also works on arm32, and
> > therefore the docs should work for both cases. However...
> There is one issue with it, please see below.
>
> > > Signed-off-by: Viktor Mitin <viktor_mitin@xxxxxxxx>
> > > ---
> > >    docs/features/dom0less.pandoc | 29 +++++++++++++++++++++--------
> > >    1 file changed, 21 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/docs/features/dom0less.pandoc b/docs/features/dom0less.pandoc
> > > index e076e3739e..961813696f 100644
> > > --- a/docs/features/dom0less.pandoc
> > > +++ b/docs/features/dom0less.pandoc
> > > @@ -62,19 +62,19 @@ device tree adding a node under /chosen as follows:
> > >
> > >        domU1 {
> > >            compatible = "xen,domain";
> > > -        memory = <0x20000>;
> > > +        memory = <0x0 0x20000>; >           cpus = 1;
> > >            vpl011;
> > >
> > >            module@2000000 {
> > >                compatible = "multiboot,kernel", "multiboot,module";
> > > -            reg = <0x2000000 0xffffff>;
> > > +            reg = <0x0 0x2000000 0x0 0xffffff>;
> > ... nothing on arm64 impose #address-cells = 2 and #size-cells = 2. The
> > problem here is the two properties are missing in the node domU1.
> The next issue was observed with arm64 (arm32 was not tested).
> The reg properties inside 'module' nodes are ok either with additional '0x0'
> or with #address-cells = 2 and #size-cells = 2.
>
> However, the 'memory' property does not work without additional '0x0'
> and #address-cells = 2 and #size-cells = 2 don't affect it.
> The next code fails without '0x0'. This was the reason why I added '0x0'
> and not #address-cells = 2 and #size-cells = 2. Now it is clear that
> we need to use
> #address-cells and #size-cells anyway, however, I'm not sure about
> memory property.
> Should it be with extra zero anyway for both cases arm32 and arm64?
>
> memory = <0x0 0x20000>;
Per the documentation (docs/misc/arm/device-tree/booting.txt):

"- memory

A 64-bit integer specifying the amount of kilobytes of RAM to
allocate to the guest.
"

So memory is always a 64-bit integer and therefore is described using 2 
cells.
Cheers,

--
Julien Grall

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