Re: [RFC PATCH 08/19] HostMem: Add private property to indicate to use kvm gmem

[David Hildenbrand <david@redhat.com>]

On 31.07.23 18:21, Xiaoyao Li wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>   backends/hostmem.c       | 18 ++++++++++++++++++
>   include/sysemu/hostmem.h |  2 +-
>   qapi/qom.json            |  4 ++++
>   3 files changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/backends/hostmem.c b/backends/hostmem.c
> index 747e7838c031..dbdbb0aafd45 100644
> --- a/backends/hostmem.c
> +++ b/backends/hostmem.c
> @@ -461,6 +461,20 @@ static void host_memory_backend_set_reserve(Object *o, bool value, Error **errp)
>       }
>       backend->reserve = value;
>   }
> +
> +static bool host_memory_backend_get_private(Object *o, Error **errp)
> +{
> +    HostMemoryBackend *backend = MEMORY_BACKEND(o);
> +
> +    return backend->private;
> +}
> +
> +static void host_memory_backend_set_private(Object *o, bool value, Error **errp)
> +{
> +    HostMemoryBackend *backend = MEMORY_BACKEND(o);
> +
> +    backend->private = value;
> +}
>   #endif /* CONFIG_LINUX */
>   
>   static bool
> @@ -541,6 +555,10 @@ host_memory_backend_class_init(ObjectClass *oc, void *data)
>           host_memory_backend_get_reserve, host_memory_backend_set_reserve);
>       object_class_property_set_description(oc, "reserve",
>           "Reserve swap space (or huge pages) if applicable");
> +    object_class_property_add_bool(oc, "private",
> +        host_memory_backend_get_private, host_memory_backend_set_private);
> +    object_class_property_set_description(oc, "private",
> +        "Use KVM gmem private memory");
>   #endif /* CONFIG_LINUX */
>       /*
>        * Do not delete/rename option. This option must be considered stable
> diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
> index 39326f1d4f9c..d88970395618 100644
> --- a/include/sysemu/hostmem.h
> +++ b/include/sysemu/hostmem.h
> @@ -65,7 +65,7 @@ struct HostMemoryBackend {
>       /* protected */
>       uint64_t size;
>       bool merge, dump, use_canonical_path;
> -    bool prealloc, is_mapped, share, reserve;
> +    bool prealloc, is_mapped, share, reserve, private;
>       uint32_t prealloc_threads;
>       ThreadContext *prealloc_context;
>       DECLARE_BITMAP(host_nodes, MAX_NODES + 1);
> diff --git a/qapi/qom.json b/qapi/qom.json
> index 7f92ea43e8e1..e0b2044e3d20 100644
> --- a/qapi/qom.json
> +++ b/qapi/qom.json
> @@ -605,6 +605,9 @@
>   # @reserve: if true, reserve swap space (or huge pages) if applicable
>   #     (default: true) (since 6.1)
>   #
> +# @private: if true, use KVM gmem private memory
> +#           (default: false) (since 8.1)
> +#

But that's not what any of this does.

This patch only adds a property and doesn't even explain what it intends 
to achieve with that.

How will it be used from a user? What will it affect internally? What 
will it modify in regards of the memory backend?

That all should go into the surprisingly empty patch description.

-- 
Cheers,

David / dhildenb