Re: [QEMU-devel][RFC PATCH 1/1] backends/hostmem: qapi/qom: Add an ObjectOption for memory-backend-* called HostMemType and its arg 'cxlram'

[Markus Armbruster]

QAPI schema sanity review only.

"Ho-Ren (Jack) Chuang" <horenchuang@bytedance.com> writes:

> Introduce a new configuration option 'host-mem-type=' in the
> '-object memory-backend-ram', allowing users to specify
> from which type of memory to allocate.
>
> Users can specify 'cxlram' as an argument, and QEMU will then
> automatically locate CXL RAM NUMA nodes and use them as the backend memory.
> For example:
>       -object memory-backend-ram,id=vmem0,size=19G,host-mem-type=cxlram \
>       -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
>       -device cxl-rp,port=0,bus=cxl.1,id=root_port13,chassis=0,slot=2 \
>       -device cxl-type3,bus=root_port13,volatile-memdev=vmem0,id=cxl-vmem0 \
>       -M 
> cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=19G,cxl-fmw.0.interleave-granularity=8k
>  \
>
> In v1, we plan to move most of the implementations to util and break down
> this patch into different smaller patches.
>
> Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@bytedance.com>
> Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>

[...]

> diff --git a/qapi/common.json b/qapi/common.json
> index 6fed9cde1a..591fd73291 100644
> --- a/qapi/common.json
> +++ b/qapi/common.json
> @@ -167,6 +167,25 @@
>  { 'enum': 'HostMemPolicy',
>    'data': [ 'default', 'preferred', 'bind', 'interleave' ] }
>  
> +##
> +# @HostMemType:
> +#
> +# Automatically find a backend memory type on host.

Types don't do, they are.  Suggest something like

   # Host memory types

> +# Can be further extened to support other types such as cxlpmem, hbm.

Doc comments are reference documentation for users of QMP.  This
sentence doesn't fit there.

> +#
> +# @none: do nothing (default).

Again, types don't do, they are.

(default) makes no sense here.  Types don't have defaults, optional
arguments do.  In this case, @host-mem-type below.

What kind of memory does this setting request?

> +#
> +# @cxlram: a CXL RAM backend on host.

Suggest to spell it cxl-ram.

> +#
> +# Note: HostMemType and HostMemPolicy/host-nodes cannot be set at the same
> +# time. HostMemType is used to automatically bind with one kind of
> +# host memory types.

I feel this note doesn't belong here.  Add it to the users of
HostMemType and HostMemPolicy instead.

> +#
> +# Since: 8.3
> +##
> +{ 'enum': 'HostMemType',
> +  'data': [ 'none', 'cxlram' ] }
> +

I guess you're adding this to common.json and not qom.json so it's next
to HostMemPolicy.  Okay.

>  ##
>  # @NetFilterDirection:
>  #
> diff --git a/qapi/qom.json b/qapi/qom.json
> index 95516ba325..fa3bc29708 100644
> --- a/qapi/qom.json
> +++ b/qapi/qom.json
> @@ -626,6 +626,7 @@
>              '*host-nodes': ['uint16'],
>              '*merge': 'bool',
>              '*policy': 'HostMemPolicy',
> +            '*host-mem-type': 'HostMemType',
>              '*prealloc': 'bool',
>              '*prealloc-threads': 'uint32',
>              '*prealloc-context': 'str',

Missing: doc comment update.

[...]