Re: [Qemu-devel] [PATCH v3 1/3] pc-dimm: factor out MemoryDevice interface

[David Gibson <david@gibson.dropbear.id.au>]

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On Sun, Apr 22, 2018 at 10:21:34AM +0200, David Hildenbrand wrote:
> On 22.04.2018 06:26, David Gibson wrote:
> > On Fri, Apr 20, 2018 at 02:34:54PM +0200, David Hildenbrand wrote:
> >> On the qmp level, we already have the concept of memory devices:
> >>     "query-memory-devices"
> >> Right now, we only support NVDIMM and PCDIMM.
> >>
> >> We want to map other devices later into the address space of the guest.
> >> Such device could e.g. be virtio devices. These devices will have a
> >> guest memory range assigned but won't be exposed via e.g. ACPI. We want
> >> to make them look like memory device, but not glued to pc-dimm.
> >>
> >> Especially, it will not always be possible to have TYPE_PC_DIMM as a parent
> >> class (e.g. virtio devices). Let's use an interface instead. As a first
> >> part, convert handling of
> >> - qmp_pc_dimm_device_list
> >> - get_plugged_memory_size
> >> to our new model. plug/unplug stuff etc. will follow later.
> >>
> >> A memory device will have to provide the following functions:
> >> - get_addr(): Necessary, as the property "addr" can e.g. not be used for
> >>               virtio devices (already defined).
> >> - get_plugged_size(): The amount this device offers to the guest as of
> >>                       now.
> >> - get_region_size(): Because this can later on be bigger than the
> >>                      plugged size.
> >> - fill_device_info(): Fill MemoryDeviceInfo, e.g. for qmp.
> >>
> >> Signed-off-by: David Hildenbrand <david@redhat.com>
> > 
> > Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> > 
> > with the exception of some tiny nits..
> > 
> > [snip]
> >> +static gint memory_device_addr_sort(gconstpointer a, gconstpointer b)
> >> +{
> >> +    MemoryDeviceState *md_a = MEMORY_DEVICE(a);
> >> +    MemoryDeviceState *md_b = MEMORY_DEVICE(b);
> > 
> > These probably should be const MemoryDeviceState *.
> 
> Yes, that could work (depends on what the functions getting called
> internally expect). Will look into it

Well, the only thing being called here is the ->get_addr() hook, which
you can redefine if necessary.  Discarding the const in the passed in
pointers seems like bad idea, even though it won't explicitly warn due
to the existing MEMORY_DEVICE() cast.

> >> +    MemoryDeviceClass *mdc_a = MEMORY_DEVICE_GET_CLASS(a);
> >> +    MemoryDeviceClass *mdc_b = MEMORY_DEVICE_GET_CLASS(b);
> >> +    const uint64_t addr_a = mdc_a->get_addr(md_a);
> >> +    const uint64_t addr_b = mdc_b->get_addr(md_b);
> >> +
> >> +    if (addr_a > addr_b) {
> >> +        return 1;
> >> +    } else if (addr_a < addr_b) {
> >> +        return -1;
> >> +    }
> >> +    return 0;
> >> +}
> >> +
> >> +static int memory_device_built_list(Object *obj, void *opaque)
> > 
> > s/built/build/ will read a bit more clearly I think.
> > 
> 
> Indeed, thanks!
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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