Re: [RFC PATCH 12/21] i386/xen: set shared_info page

[David Woodhouse <dwmw2@infradead.org>]

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On Mon, 2022-12-05 at 23:17 +0100, Philippe Mathieu-Daudé wrote:
> On 5/12/22 18:31, David Woodhouse wrote:
> > From: Joao Martins <joao.m.martins@oracle.com>
> > 
> > This is done by implementing HYPERVISOR_memory_op specifically
> > XENMEM_add_to_physmap with space XENMAPSPACE_shared_info. While
> > Xen removes the page with its own, we instead use the gfn passed
> > by the guest.
> > 
> > Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> > Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> > ---
> >   accel/kvm/kvm-all.c      |  6 ++++
> >   include/hw/core/cpu.h    |  2 ++
> >   include/sysemu/kvm.h     |  2 ++
> >   include/sysemu/kvm_int.h |  3 ++
> >   target/i386/cpu.h        |  8 ++++++
> >   target/i386/trace-events |  1 +
> >   target/i386/xen-proto.h  | 19 +++++++++++++
> >   target/i386/xen.c        | 61 ++++++++++++++++++++++++++++++++++++++++
> >   8 files changed, 102 insertions(+)
> >   create mode 100644 target/i386/xen-proto.h
> 
> 
> > diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> > index 8830546121..e57b693528 100644
> > --- a/include/hw/core/cpu.h
> > +++ b/include/hw/core/cpu.h
> > @@ -443,6 +443,8 @@ struct CPUState {
> >   
> >       /* track IOMMUs whose translations we've cached in the TCG TLB */
> >       GArray *iommu_notifiers;
> > +
> > +    struct XenState *xen_state;
> 
> Since you define a type definition below, use it.

Ack.

More importantly though, some of that state needs to be persisted
across live migration / live update. 

There is per-vCPU state (the GPAs for vcpu_info etc., upcall vector,
timer info). I think I see how I could add that to the vmstate_x86_cpu
defined in target/i386/machine.c.

For the machine-wide state, where do I add that? Should I just
instantiate a dummy device (a bit like TYPE_KVM_CLOCK, AFAICT) to hang
that state off? 

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