Re: [Xen-devel] [PATCH v3] xen/doc: Improve Dom0-less documentation

[Julien Grall <julien.grall@xxxxxxx>]

Hi Viktor,

On 7/10/19 6:18 AM, Viktor Mitin wrote:
> - Changed unprintable characters with %s/\%xA0/ /g
>    So all the spaces are 0x20 now.
>
> - Added address-cells and size-cells to configuration example.
>    This resolves the dom0less boot issue in case of arm64.
>
> - Added some notes about xl tools usage in case of dom0less.
>
> - Added extra 0x0 to memory property in configuration example.
>    This matches the binding docs/misc/arm/device-tree/booting.txt
>    which requires a 64-bit value.
>
> Signed-off-by: Viktor Mitin <viktor_mitin@xxxxxxxx>
> ---
>
> v3:
> - Added extra 0x0 to memory property in configuration example.
>    This matches the binding docs/misc/arm/device-tree/booting.txt
>    which requires a 64-bit value.
> ---
>   docs/features/dom0less.pandoc | 58 +++++++++++++++++++++++------------
>   1 file changed, 39 insertions(+), 19 deletions(-)
>
> diff --git a/docs/features/dom0less.pandoc b/docs/features/dom0less.pandoc
> index e076e3739e..d4f44b5502 100644
> --- a/docs/features/dom0less.pandoc
> +++ b/docs/features/dom0less.pandoc
> @@ -40,8 +40,8 @@ to boot. For example if this is the bootcmd for Xen and Dom0:
>
>       bootm 0x1400000 0x9000000 0x1280000
>
> -If we want to add one DomU with Image-DomU as the DomU kernel
> -and ramdisk-DomU as DomU ramdisk:
> +If we want to add one DomU with Image-DomU as the DomU kernel
> +and ramdisk-DomU as DomU ramdisk:
>
>       tftpb 0x1280000 xen.dtb
>       tftpb 0x80000 xen-Image
> @@ -61,25 +61,27 @@ the presence of the additional VM and its configuration. It 
> is done via
>   device tree adding a node under /chosen as follows:
>
>       domU1 {
> -        compatible = "xen,domain";
> -        memory = <0x20000>;
> -        cpus = 1;
> -        vpl011;
> -
> -        module@2000000 {
> -            compatible = "multiboot,kernel", "multiboot,module";
> -            reg = <0x2000000 0xffffff>;
> -            bootargs = "console=ttyAMA0";
> -        };
> -
> -        module@30000000 {
> -            compatible = "multiboot,ramdisk", "multiboot,module";
> -            reg = <0x3000000 0xffffff>;
> -        };
> +        #address-cells = <0x00000001>;
> +        #size-cells = <0x00000001>;
DTC is can deal with decimal number. So I would prefer if we directly 
use 1 in the 2 properties above.
> +        compatible = "xen,domain";
> +        memory = <0x0 0x20000>;
> +        cpus = 1;
I think this should be cpus = <1>;

> +        vpl011;
> +
> +        module@2000000 {
> +            compatible = "multiboot,kernel", "multiboot,module";
> +            reg = <0x2000000 0xffffff>;
> +            bootargs = "console=ttyAMA0";
> +        };
> +
> +        module@30000000 {
> +            compatible = "multiboot,ramdisk", "multiboot,module";
> +            reg = <0x3000000 0xffffff>;
> +        };
>       };
>
> -Where memory is the memory of the VM in KBs, cpus is the number of
> -cpus. module@2000000 and module@3000000 advertise where the kernel and
> +Where memory is the memory of the VM in KBs, cpus is the number of
> +cpus. module@2000000 and module@3000000 advertise where the kernel and
>   ramdisk are in memory.
As a side note, the size specified should exactly match the size of the 
Kernel/initramfs. Otherwise, they may be unusable in Xen (for instance 
if they are compressed).
>   See docs/misc/arm/device-tree/booting.txt for more information.
> @@ -111,3 +113,21 @@ limitations:
>     the Xen command line. The NULL scheduler automatically assigns and
>     pins vCPUs to pCPUs, but the vCPU-pCPU assignments cannot be
>     configured.
> +
> +Notes
> +-----
> +
> +- 'xl console' command will not attach to the domain's console in case
> +  of dom0less. DomU are domains created by Xen (similar to Dom0) and
> +  therefore they are all managed by Xen and some of the commands may not work.
> +
> +  A user is allowed to configure the key sequence to switch input.
> +  Pressing the Xen "conswitch" (Ctrl-A by default) three times
> +  switches input in case of dom0less mode.
> +
> +- Domains created by Xen will have no name at boot. Domain-0 has a name
> +  thanks to the helper xen-init-dom0 called at boot by the initscript.
> +  If you want to setup DomU name, then you will have to create the xenstore
> +  node associated. By default DomU names are shown as '(null)' in the
> +  xl domains list.
> +
Except the few minors things above. The improvement looks good to me, 
although I would like another pair of eye. Stefano, can you look at it?
Cheers,

--
Julien Grall

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