The main feature of FORM2 affinity support is the separation of NUMA
distances from ibm,associativity information. This allows for a more
flexible and straightforward NUMA distance assignment without relying on
complex associations between several levels of NUMA via
ibm,associativity matches. Another feature is its extensibility. This base
support contains the facilities for NUMA distance assignment, but in the
future more facilities will be added for latency, performance, bandwidth
and so on.
This patch implements the base FORM2 affinity support as follows:
- the use of FORM2 associativity is indicated by using bit 2 of byte 5
of ibm,architecture-vec-5. A FORM2 aware guest can choose to use FORM1
or FORM2 affinity. Setting both forms will default to FORM2. We're not
advertising FORM2 for pseries-6.1 and older machine versions to prevent
guest visible changes in those;
- ibm,associativity-reference-points has a new semantic. Instead of
being used to calculate distances via NUMA levels, it's now used to
indicate the primary domain index in the ibm,associativity domain of
each resource. In our case it's set to {0x4}, matching the position
where we already place logical_domain_id;
- two new RTAS DT artifacts are introduced: ibm,numa-lookup-index-table
and ibm,numa-distance-table. The index table is used to list all the
NUMA logical domains of the platform, in ascending order, and allows for
spartial NUMA configurations (although QEMU ATM doesn't support that).
ibm,numa-distance-table is an array that contains all the distances from
the first NUMA node to all other nodes, then the second NUMA node
distances to all other nodes and so on;
- get_max_dist_ref_points(), get_numa_assoc_size() and get_associativity()
now checks for OV5_FORM2_AFFINITY and returns FORM2 values if the guest
selected FORM2 affinity during CAS.
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20210920174947.556324-7-danielhb413@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
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