Bug 1344497

+++ This bug was initially created as a clone of Bug #1344494 +++

+++ This bug was initially created as a clone of Bug #1344450 +++

Description of problem:
Partner uses information in the SLIT table to make NUMA placement decisions in their application.  Without accurate information, performance can be impacted.

Passing the correct SLIT table information from the host to the guest seems to make sense as long as the CPUs are pinned in a 1-to-1 fashion between the host and guest.  If the guest consumes all the numa nodes, then the whole table could be passed.  In the case of a guest using only a subset of nodes, the appropriate section (or sections) of the host SLIT table could be used.

The following example is from an 8-socket SGI system (this is not unique to this system however):

Host> numactl -H
…

node   0   1   2   3   4   5   6   7
  0:  10  16  19  16  50  50  50  50
  1:  16  10  16  19  50  50  50  50
  2:  19  16  10  16  50  50  50  50
  3:  16  19  16  10  50  50  50  50
  4:  50  50  50  50  10  16  19  16
  5:  50  50  50  50  16  10  16  19
  6:  50  50  50  50  19  16  10  16
  7:  50  50  50  50  16  19  16  10
 
-------------------------------------------------


Guest> numactl -H
…

node   0   1   2   3   4   5   6   7
  0:  10  20  20  20  20  20  20  20
  1:  20  10  20  20  20  20  20  20
  2:  20  20  10  20  20  20  20  20
  3:  20  20  20  10  20  20  20  20
  4:  20  20  20  20  10  20  20  20
  5:  20  20  20  20  20  10  20  20
  6:  20  20  20  20  20  20  10  20
  7:  20  20  20  20  20  20  20  10


Version-Release number of selected component (if applicable):
Host and guest - RHEL 7.2
qemu-kvm-rhev  10:2.3.0-31

How reproducible:


Steps to Reproduce:
1. Create a guest, pin host and guest CPUs on a 1-to-1 basis
2. Run numactl -H command on host and guest and compare


Actual results:
SLIT tables are different between host and guest

Expected results:
Whole SLIT table or appropriate section of SLIT table in guest and host are the same

Additional info:

--- Additional comment from Karen Noel on 2016-06-09 15:25:14 EDT ---

The NUMA topology is set up by libvirt, while the slit table lives in the guest firmware. 

Should the slit table change after live migration if the destination host is different? I think so, but guests may not expect a dynamic slit table. Application may have to modified to take migration into account.