Re: [PATCH RFC] x86/hvm: unify HVM and PVH hypercall tables.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Thu, May 15, 2014 at 04:35:57PM -0700, Mukesh Rathor wrote:
> On Thu, 15 May 2014 10:32:24 -0400
> Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
> 
> > 
> > On May 15, 2014 6:30 AM, Tim Deegan <tim@xen.org> wrote:
> > >
> > > At 14:39 -0400 on 08 May (1399556383), Konrad Rzeszutek Wilk wrote: 
> > > > On Thu, May 08, 2014 at 04:31:30PM +0100, Tim Deegan wrote: 
> > > > > Stage one of many in merging PVH and HVM code in the
> > > > > hypervisor. 
> > > > > 
> > > > > This exposes a few new hypercalls to HVM guests, all of which
> > > > > were already available to PVH ones: 
> > > > > 
> > > > >  - XENMEM_memory_map / XENMEM_machine_memory_map /
> > > > >XENMEM_machphys_mapping: These are basically harmless, if a bit
> > > > >useless to plain HVM. 
> > > > > 
> > > > >  - VCPUOP_send_nmi / VCPUOP_initialise / VCPUOP[_is]_up /
> > > > >VCPUOP_down This will eventually let HVM guests bring up APs the
> > > > >way PVH ones do. For now, the VCPUOP_initialise paths are still
> > > > >gated on is_pvh. 
> > > > 
> > > > I had a similar patch to enable this under HVM and found out that 
> > > > if the guest issues VCPUOP_send_nmi we get in Linux: 
> > > > 
> > > > [    3.611742] Corrupted low memory at c000fffc (fffc phys) =
> > > > 00029b00 [    2.386785] Corrupted low memory at ffff88000000fff8
> > > > (fff8 phys) = 2990000000000 
> > > > 
> > > > http://mid.gmane.org/20140422183443.GA6817@phenom.dumpdata.com 
> > >
> > > Right, thanks.  Do you think that's likely to be a hypervisor bug,
> > > or just a "don't do that then"?
> > 
> > It is a bug. But I don't know where and had not had a chance to
> > investigate this further.
> > 
> > My feeling is that it is APIC emulation but I might be quite off.
> > >
> > > AFAICT PVH domains need this as they have no other way of sending 
> > > NMIs. 
> > >
> > 
> > Perhaps. The vAPIC that Boris had been looking at could make this
> > work via the APIC path.
> 
> But, VCPUOP_send_nmi works for PVH right, and only HVM has problem?

I did not test PVH - just tried with HVM. It might be that the PVH
won't have the issue.
> 
> mukesh
>