Re: [PATCH v8 11/14] hw/cxl/events: Add qmp interfaces to add/release dynamic capacity extents

[Ira Weiny <ira.weiny@intel.com>]

Alireza Sanaee wrote:
> On Thu, 23 May 2024 10:44:51 -0700
> nifan.cxl@gmail.com wrote:
> 
> > From: Fan Ni <fan.ni@samsung.com>
> > 
> > To simulate FM functionalities for initiating Dynamic Capacity Add
> > (Opcode 5604h) and Dynamic Capacity Release (Opcode 5605h) as in CXL
> > spec r3.1 7.6.7.6.5 and 7.6.7.6.6, we implemented two QMP interfaces
> > to issue add/release dynamic capacity extents requests.
> > 
> > With the change, we allow to release an extent only when its DPA range
> > is contained by a single accepted extent in the device. That is to
> > say, extent superset release is not supported yet.
> > 
> > 1. Add dynamic capacity extents:
> > 
> > For example, the command to add two continuous extents (each 128MiB
> > long) to region 0 (starting at DPA offset 0) looks like below:
> > 
> > { "execute": "qmp_capabilities" }
> > 
> > { "execute": "cxl-add-dynamic-capacity",
> >   "arguments": {
> >       "path": "/machine/peripheral/cxl-dcd0",
> >       "host-id": 0,
> >       "selection-policy": "prescriptive",
> >       "region": 0,
> >       "extents": [
> >       {
> >           "offset": 0,
> >           "len": 134217728
> >       },
> >       {
> >           "offset": 134217728,
> >           "len": 134217728
> >       }
> >       ]
> >   }
> > }
> > 
> > 2. Release dynamic capacity extents:
> > 
> > For example, the command to release an extent of size 128MiB from
> > region 0 (DPA offset 128MiB) looks like below:
> > 
> > { "execute": "cxl-release-dynamic-capacity",
> >   "arguments": {
> >       "path": "/machine/peripheral/cxl-dcd0",
> >       "host-id": 0,
> >       "removal-policy":"prescriptive",
> >       "region": 0,
> >       "extents": [
> >       {
> >           "offset": 134217728,
> >           "len": 134217728
> >       }
> >       ]
> >   }
> > }
> > 
> > Tested-by: Svetly Todorov <svetly.todorov@memverge.com>
> > Reviewed-by: Gregory Price <gregory.price@memverge.com>
> > Signed-off-by: Fan Ni <fan.ni@samsung.com>

[snip]

> > +##
> > +# @cxl-release-dynamic-capacity:
> > +#
> > +# Command to initiate to release dynamic capacity extents from a
> > +# host.  It simulates operations defined in cxl spec r3.1 7.6.7.6.6.
> > +#
> > +# @path: CXL DCD canonical QOM path.
> > +#
> > +# @host-id: The "Host ID" field as defined in cxl spec r3.1
> > +#     Table 7-71.
> > +#
> > +# @removal-policy: Bit[3:0] of the "Flags" field as defined in cxl
> > +#     spec r3.1 Table 7-71.
> > +#
> > +# @forced-removal: Bit[4] of the "Flags" field in cxl spec r3.1
> > +#     Table 7-71.  When set, device does not wait for a Release
> > +#     Dynamic Capacity command from the host.  Host immediately
> > +#     loses access to released capacity.
> > +#
> > +# @sanitize-on-release: Bit[5] of the "Flags" field in cxl spec r3.1
> > +#     Table 7-71.  When set, device should sanitize all released
> > +#     capacity as a result of this request.
> > +#
> > +# @region: The "Region Number" field as defined in cxl spec r3.1
> > +#     Table 7-71.  The dynamic capacity region where the capacity
> > +#     is being added.  Valid range is from 0-7.
> > +#
> > +# @tag: The "Tag" field as defined in cxl spec r3.1 Table 7-71.
> > +#
> > +# @extents: The "Extent List" field as defined in cxl spec r3.1
> > +#     Table 7-71.
> > +#
> > +# Since : 9.1
> > +##
> > +{ 'command': 'cxl-release-dynamic-capacity',
> > +  'data': { 'path': 'str',
> > +            'host-id': 'uint16',
> > +            'removal-policy': 'CXLExtRemovalPolicy',
> > +            '*forced-removal': 'bool',
> > +            '*sanitize-on-release': 'bool',
> > +            'region': 'uint8',
> > +            '*tag': 'str',
> > +            'extents': [ 'CXLDynamicCapacityExtent' ]
> > +           }
> > +}
> 
> Although tag-based removal is not implemented yet, but still just wanted
> to leave a comment here that exact extents are not needed for tag-based
> removal and `extents` should be an optional parameter here; this is my
> understanding reading the spec, so I still might be wrong, shout if you
> think it does not make sense.

It's been a while but I think this allows the removal of non-tagged
extents as well(?)  If so the tag would be NULL (or empty-string) and one
can remove a regular extent.

But I could be miss-remembering something,
Ira