Re: [Xen-devel] [PATCH RFC v12 07/21] pvh: Disable unneeded features of HVM containers

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

On Fri, 13 Sep 2013 17:36:06 +0100
George Dunlap <george.dunlap@xxxxxxxxxxxxx> wrote:

> On 13/09/13 17:25, George Dunlap wrote:
> > Things kept:
> > * cacheattr_region lists
> > * irq-related structures
> > * paging
> > * tm_list
> >
> > Things disabled for now:
> > * compat xlation
> >
> > Things disabled:
> > * Emulated timers and clock sources
> > * IO/MMIO emulation
> > * msix tables
> > * hvm params
> > * hvm_funcs
......
> > unsigned long gfn, mfn_t mfn, ((d->vcpu == NULL) || ((v =
> > d->vcpu[0]) == NULL)) ) return MTRR_TYPE_WRBACK;
> >   
> > -    if ( !v->domain->arch.hvm_domain.params[HVM_PARAM_IDENT_PT] )
> > +    if ( v->domain->arch.hvm_domain.params
> > +
> > && !v->domain->arch.hvm_domain.params[HVM_PARAM_IDENT_PT] )
> 
> This is one thing I want to discuss: I can see why initially it was 
> decided to disable hvm_params, as at the moment PVH only uses one of 
> them, and this saves allocating the array for PVH domains.  But the 
> result is a lot of fairly ugly things like this.  There's also (in 
> another patch) a hack that allows a guest to *set* the IRQ callback
> via hvmop hvm_param_set, but not *read* it.
> 
> Additionally, as far as I can tell, the only reason we can't support
> mem events is because we don't have hvm_params.
> 
> Since I think at some point we well want to use the mem events on PVH 
> guests, we should probably just allocate it now and avoid having
> things like this in the first place.

That would work too. My goal was to add things incrementally so they
got properly tested.

Mukesh


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