RE: [Xen-devel] Re: Xen/ia64 status (and solicitation for alpha testers and developers)

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

> Out of interest, what are the modifications likely to look 
> like in terms of 
> the source tree?  Will it be necessary to introduce a new 
> (sub?) architecture 
> to Linux in order to incorporate them?

On vBlades, no changes were required to common linux files
and there were two kinds of changes to ia64 archdep, intrusive
and new files.  The intrusive changes required a patch of about
80 lines IIRC and all the changes were "transparent" (e.g.
the linux kernel worked both natively on bare metal and on top
of the VMM), which is my intent for Xen/ia64 as well.
In addition there were several new files that needed to be linked
in (including a paravirtualized version of ivt.S which is a very
complicated assembly file).

This was all on linux-2.4.xx.  We'll see about linux-2.6 soon.

For this low magnitude of change, a new subarch seems unnecessary,
but it could go either way, depending on Linux community
feedback.
 
> Also, do you / will you support legacy IA-32 code?

To the extent that Linux/ia64 does, yes.  There is currently one
privilege-sensitive register that is required that I did not
implement yet (and is used at startup if CONFIG_IA32_SUPPORT
is enabled) and it is all totally untested so it is currently
turned off, but I don't foresee any major problems.

> Sorry for all the questions.  Xen on IA-64 looks very cool stuff!

Thanks!  We're working on getting some equipment to Cambridge
so Xen/ia64 can be included in the regular Xen build/test process
early next year.

Dan


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