Re: [Xen-devel] PVH: domain creations...

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2012-11-21 at 02:26 +0000, Mukesh Rathor wrote:
> Hi guys,
> 
> Good news, I got everything working on my refreshed tree. So, now time
> to clean up the patch, look at the fixme's/TBDs to see what needs to be
> done in phase I and what can be deferred. Lets start with domain
> creation:
> 
> I currently have following for domain creation:
>   dom0: dom0pvh in the command line makes it PVH mode. IMO, we should leave
>         this as is until PVH is default.
> 
>   domU: vm.cfg has line: is_pvh = 1. The tools then parse this and set
>         is_pvh fields in  libxl_domain_create_info{} and
>         libxl_domain_build_info{}. I also introduced XEN_DOMCTL_CDF_pvh_guest 
>         flag to send down the info to xen during domU creation.
>  
> 
>  1. I suppose in XEN_DOMCTL_createdomain in xen: I could just see if
>  it's PV guest with HAP, ie, 
>        if (~XEN_DOMCTL_CDF_hvm_guest && XEN_DOMCTL_CDF_hap)
>             then domcr_flags |= DOMCRF_pvh;
> 
>    This would result in elimination of XEN_DOMCTL_CDF_pvh_guest flag.
>    What do you think?

Seems to make sense. And this interface is a hyp<=>tools one so we can
always fix it or change it if necessary.

(one thought for the future would be to include the kernels feature
flags in struct xen_domctl_createdomain, for example)

>  2. I suppose I could undo flags in libxl_domain_create_info and 
>     libxl_domain_build_info, and just call xc_dom_feature_translated()
>     and assume it's PVH if it returns true for PV?

I think you actually want both, i.e. libxl/libxc should provide a
sensible default (perhaps based on xc_dom_feature_translated as you
suggest) but you also want a way for the user to forcibly enable or
disable it in the guest config (to workaround bugs, allow comparative
benchmarks etc).

> Also, I realized SIF_IS_PVH is probably not needed and I'm trying to 
> see if I can remove it.

Cool.

Ian.


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