Re: [Xen-users] Converting a HVM Guest into a PV-on-HVM Guest

[Srujan Kotikela <ksrujandas@xxxxxxxxx>]

forgot to cc, earlier.

On Mon, Jun 20, 2011 at 9:22 PM, Srujan Kotikela <ksrujandas@xxxxxxxxx> wrote:

Hi Todd,

Thanks for the reply.

I am trying to invoke a hypercall from the HVM guest. The only way I did hypercalls from DomU till now (on PV guests) is use the libxc library do_xen_hypercall (which in turn uses do_privcmd which in turn uses ioctl). 

Now I have a added a custom hypercall to xen and I am trying to invoke it from HVM guest. As the HVM guest is not xenified (-linux) it doesn't have the privcmd interface (/proc/xen/privcmd). So I am looking for a way to invoke the custom hypercall from HVM. While in this try, I found that pv-on-hvm will enable hypercalls from HVM guest. However I also read that it may not allow all the hypercalls (correct me if I am wrong). 

While looking at the other posts I found this, http://xen.1045712.n5.nabble.com/hypercalls-from-HVM-guest-on-XEN-3-4-3-td4454566.html which recommends to look into tools/firmware/hvmloader. There is some code in hypercall.h in the hvmloader directory (http://rswiki.csie.org/lxr/http/source/tools/firmware/hvmloader/hypercall.h?v=xen-4.0.0;a=ppc). I am figuring out how to make use of this. Will update once I figure it out.

Sorry for not being unclear, earlier.

--
Srujan D. Kotikela

On Mon, Jun 20, 2011 at 8:54 PM, Todd Deshane <todd.deshane@xxxxxxx> wrote:

On Mon, Jun 20, 2011 at 2:44 PM, Srujan Kotikela <ksrujandas@xxxxxxxxx> wrote:
> Just to make sure,
>
> PV-on-HVM drivers are neccessary and/or sufficient to make hypercalls from a
> HVM domain, right?
>

I'm not sure.

A quick search indicates that there is some HVM hypercall code:

http://xen.markmail.org/search/?q=hvm+hypercall
http://xen.markmail.org/search/?q=hypercall_hvm_op#query:hypercall_hvm_op+page:1+mid:bozac75eaw4jrgof+state:results
http://lxr.xensource.com/lxr/source/xen/arch/x86/hvm/hvm.c

I don't know the details. You may considering taking a look at:
http://wiki.xensource.com/xenwiki/AskingXenDevelQuestions

Thanks,
Todd

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