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    Subject[PATCH 4.4 116/158] powerpc/pseries/mobility: prevent cpu hotplug during DT update
    Date
    [ Upstream commit e59a175faa8df9d674247946f2a5a9c29c835725 ]

    CPU online/offline code paths are sensitive to parts of the device
    tree (various cpu node properties, cache nodes) that can be changed as
    a result of a migration.

    Prevent CPU hotplug while the device tree potentially is inconsistent.

    Fixes: 410bccf97881 ("powerpc/pseries: Partition migration in the kernel")
    Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
    Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/platforms/pseries/mobility.c | 9 +++++++++
    1 file changed, 9 insertions(+)

    diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
    index c773396d0969..fcd1a32267c4 100644
    --- a/arch/powerpc/platforms/pseries/mobility.c
    +++ b/arch/powerpc/platforms/pseries/mobility.c
    @@ -9,6 +9,7 @@
    * 2 as published by the Free Software Foundation.
    */

    +#include <linux/cpu.h>
    #include <linux/kernel.h>
    #include <linux/kobject.h>
    #include <linux/smp.h>
    @@ -309,11 +310,19 @@ void post_mobility_fixup(void)
    if (rc)
    printk(KERN_ERR "Post-mobility activate-fw failed: %d\n", rc);

    + /*
    + * We don't want CPUs to go online/offline while the device
    + * tree is being updated.
    + */
    + cpus_read_lock();
    +
    rc = pseries_devicetree_update(MIGRATION_SCOPE);
    if (rc)
    printk(KERN_ERR "Post-mobility device tree update "
    "failed: %d\n", rc);

    + cpus_read_unlock();
    +
    /* Possibly switch to a new RFI flush type */
    pseries_setup_rfi_flush();

    --
    2.20.1


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