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    Subject[PATCH 5.1 163/405] powerpc/numa: improve control of topology updates
    Date
    [ Upstream commit 2d4d9b308f8f8dec68f6dbbff18c68ec7c6bd26f ]

    When booted with "topology_updates=no", or when "off" is written to
    /proc/powerpc/topology_updates, NUMA reassignments are inhibited for
    PRRN and VPHN events. However, migration and suspend unconditionally
    re-enable reassignments via start_topology_update(). This is
    incoherent.

    Check the topology_updates_enabled flag in
    start/stop_topology_update() so that callers of those APIs need not be
    aware of whether reassignments are enabled. This allows the
    administrative decision on reassignments to remain in force across
    migrations and suspensions.

    Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/mm/numa.c | 18 ++++++++++++------
    1 file changed, 12 insertions(+), 6 deletions(-)

    diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
    index f976676004ad0..48c9a97eb2c33 100644
    --- a/arch/powerpc/mm/numa.c
    +++ b/arch/powerpc/mm/numa.c
    @@ -1498,6 +1498,9 @@ int start_topology_update(void)
    {
    int rc = 0;

    + if (!topology_updates_enabled)
    + return 0;
    +
    if (firmware_has_feature(FW_FEATURE_PRRN)) {
    if (!prrn_enabled) {
    prrn_enabled = 1;
    @@ -1531,6 +1534,9 @@ int stop_topology_update(void)
    {
    int rc = 0;

    + if (!topology_updates_enabled)
    + return 0;
    +
    if (prrn_enabled) {
    prrn_enabled = 0;
    #ifdef CONFIG_SMP
    @@ -1588,11 +1594,13 @@ static ssize_t topology_write(struct file *file, const char __user *buf,

    kbuf[read_len] = '\0';

    - if (!strncmp(kbuf, "on", 2))
    + if (!strncmp(kbuf, "on", 2)) {
    + topology_updates_enabled = true;
    start_topology_update();
    - else if (!strncmp(kbuf, "off", 3))
    + } else if (!strncmp(kbuf, "off", 3)) {
    stop_topology_update();
    - else
    + topology_updates_enabled = false;
    + } else
    return -EINVAL;

    return count;
    @@ -1607,9 +1615,7 @@ static const struct file_operations topology_ops = {

    static int topology_update_init(void)
    {
    - /* Do not poll for changes if disabled at boot */
    - if (topology_updates_enabled)
    - start_topology_update();
    + start_topology_update();

    if (vphn_enabled)
    topology_schedule_update();
    --
    2.20.1


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