Re: [Xen-users] what hypercalls are supported in user-level HVM guests?

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Wed, 2015-09-23 at 10:01 +0800, Big Strong wrote:
> Hi, again. I've checked the hvm_hypercall_table in xen/arch/x86/hvm/hvm.c
> and find only 14 hypercalls available to HVM guests, much more less than
> than defined in xen/include/public/Xen.h. Here is the problem, what if I
> need a nested Xen installed in a HVM guest? Would the nested Xen only
> capable of issuing HVM hypercalls?

Yes, to the L0 hypervisor an L1 Xen is an unmodified OS, not a
paravirtualised one (unless you were to port Xen to its own PV interfaces,
which would be a large and mostly pointless exercise).

But an L1 Xen should have no need of any of the L0 PV hypercalls in order
to offer PV hypercalls to its own L2 guests. Remember it is the L1 Xen
which is responsible for implementing those hypercalls for L2 guests, it is
not the L0's responsibility.

Ian.

> 
> 2015-09-22 21:56 GMT+08:00 Big Strong <fangtuo90@xxxxxxxxx>:
> > Yes, it is. Thank you.
> > 
> > 2015-09-22 20:26 GMT+08:00 Ian Campbell <ian.campbell@xxxxxxxxxx>:
> > > On Tue, 2015-09-22 at 20:03 +0800, Big Strong wrote:
> > > > Where can I  find the hvm specific hypercall dispatch table then?
> > > I've
> > > > digged into Xen source code and found no special hypercall table
> > > for HVM,
> > > > even though there is a entry.S file under /xen/arch/x86/hvm folder,
> > > no
> > > > hypercall entries are defined there.
> > > 
> > > hvm_hypercall{32,64}_table in xen/arch/x86/hvm/hvm.c.
> > > 
> > > Ian.
> > > 
> > 

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