Re: [Xen-devel] Domain configuration for DomU

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-02-24 at 15:55 +0000, Viktor Kleinik wrote:
> We are using Linux as Dom0 and Android as DomU on OMAP5 processors 
> family. Xen version is 4.4-rc2. We have our own devtree configuration file 
> for 
> DomU. In our case device tree binary is appended to zImage by using 
> CONFIG_ARM_APPENDED_DTB option in kernel config for DomU. As I 
> understood, Xen can determine that there is appended to zImage DTB for 
> DomU. But it tries to generate its own devtree configuration file via 
> libxl__arch_domain_configure() function call thru libxl__build_pv() function 
> in 
> tools/libxl/libxl_dom.c file. Which is dummy work in that case.

This is somewhat similar to real hardware too -- the appended DTB would
override anything passed from the bootloader.

> In the same time we have some platform specific configuration which is 
> different from 
> 
> generic ARM configuration that Xen tries to generate for us. Why Xen tries 
> to generate its own devtree even if appended to zImage DTB can be 
> detected?

I think just nobody thought to stop it doing so. I'm not sure how easy
it would be to arrange it anyway -- the thing which knows about the
kernel/appending is a different library to what creates the dtb.

>  Should we expect some modifications in domain configuration 
> functions for those cases when DomU requires more platform specific 
> configuration? Please share your thoughts.

I think as features such as device passthrough get wired up properly in
the toolstack then the generated DTB should reflect this, if that is
what you are asking.

Appending a DTB really ought to become the exception not the rule.

Ian.




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