Re: [Qemu-devel] [PATCH V15 4/5] i386: add a Virtual Machine Generation ID device

[Michael S. Tsirkin]

On Thu, May 28, 2015 at 02:59:09PM +0300, Gal Hammer wrote:
> On 28/05/2015 13:25, Paolo Bonzini wrote:
> >
> >
> >On 27/04/2015 13:19, Gal Hammer wrote:
> >>+static void vmgenid_init(Object *obj)
> >>+{
> >>+    SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
> >>+    VmGenIdState *s = VMGENID(obj);
> >>+
> >>+    memory_region_init_io(&s->iomem, obj, &vmgenid_ram_ops, s, "vgid", 16);
> >
> >This is a small problem.  The spec says the memory of the VMGENID should
> >not be uncacheable, but MMIO _should_ be uncacheable.
> >
> >This is running on a VM so we maybe not care, but it's worth pointing it
> >out.
> 
> And the way I can fix it would be...? Is there another memory region I can
> use?
> 
> Thanks,
> 
>     Gal.

I think we hammered out an interesting alternative off-list: get hold of
some AddressRegionNVS memory and copy data from MMIO or port io over
there when you get an interrupt.

> >Paolo
> >
> >>+    sysbus_init_mmio(sbd, &s->iomem);
> >>+
> >>+    object_property_add_str(obj, PROPERTY_UUID, NULL, vmgenid_set_uuid, 
> >>NULL);
> >>+}
> >>+