Re: [Xen-devel] [V10 PATCH 18/23] PVH xen: add hypercall support for PVH

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

On Thu, 08 Aug 2013 08:41:04 +0100
"Jan Beulich" <JBeulich@xxxxxxxx> wrote:

> >>> On 08.08.13 at 04:12, Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
> >>> wrote:
> > On Wed, 7 Aug 2013 17:43:54 +0100
> > George Dunlap <George.Dunlap@xxxxxxxxxxxxx> wrote:
> >> On Wed, Jul 24, 2013 at 2:59 AM, Mukesh Rathor
> >> <mukesh.rathor@xxxxxxxxxx> wrote:
> >> > +static hvm_hypercall_t *const
> >> > pvh_hypercall64_table[NR_hypercalls] = {
> >> > +    HYPERCALL(platform_op),
> >> > +    HYPERCALL(memory_op),
> >> > +    HYPERCALL(xen_version),
> >> > +    HYPERCALL(console_io),
> >> > +    [ __HYPERVISOR_grant_table_op ]  = (hvm_hypercall_t
> >> > *)hvm_grant_table_op,
> >> > +    [ __HYPERVISOR_vcpu_op ]         = (hvm_hypercall_t
> >> > *)hvm_vcpu_op,
> >> > +    HYPERCALL(mmuext_op),
> >> > +    HYPERCALL(xsm_op),
> >> > +    HYPERCALL(sched_op),
> >> > +    HYPERCALL(event_channel_op),
> >> > +    [ __HYPERVISOR_physdev_op ]      = (hvm_hypercall_t
> >> > *)hvm_physdev_op,
> >> > +    HYPERCALL(hvm_op),
> >> > +    HYPERCALL(sysctl),
> >> > +    HYPERCALL(domctl)
> >> > +};
> >> 
> >> It would be nice if this list were in the same order as the other
> >> lists, so that it is easy to figure out what calls are common and
> >> what calls are different.
> > 
> > These are ordered by the hcall number, and assists in the debug.
> 
> But with George asking, do you now understand a little better
> why on a very early revision I had asked to copy either the
> HVM or PV hypercall table, and override just the entries that
> need overrides (making it very clear which ones differ)?

Like I've said before, I believe that is a poor and obfuscating way of doing
it, and I don't want my name on something I completely disagree with. It
makes code harder to read IMO. I'm adding such a
small extension to the existing HVM code, that I believe its hardly
reaching a tipping point. PVH is still evolving, this is first patch,
again, minimal changes to make a guest boot and come up in PVH mode.
Over time we'll come to understand more what other hcalls need to be
added and to what extent. At that point further enhancements can be
made... 

Mukesh

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