This option, similar to NO_HZ_FULL_ALL, simplifies configuring
a system to boot by default with all cores except the boot core
running in task isolation mode.

Signed-off-by: Chris Metcalf <cmetc...@mellanox.com>
---
 init/Kconfig       | 10 ++++++++++
 kernel/isolation.c |  6 ++++++
 2 files changed, 16 insertions(+)

diff --git a/init/Kconfig b/init/Kconfig
index 85a4b6dd26f2..2d49c5b78b93 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -813,6 +813,16 @@ config TASK_ISOLATION
         You should say "N" unless you are intending to run a
         high-performance userspace driver or similar task.
 
+config TASK_ISOLATION_ALL
+       bool "Provide task isolation on all CPUs by default (except CPU 0)"
+       depends on TASK_ISOLATION
+       help
+        If the user doesn't pass the task_isolation boot option to
+        define the range of task isolation CPUs, consider that all
+        CPUs in the system are task isolation by default.
+        Note the boot CPU will still be kept outside the range to
+        handle timekeeping duty, etc.
+
 config BUILD_BIN2C
        bool
        default n
diff --git a/kernel/isolation.c b/kernel/isolation.c
index 7cd57ca95be5..f8ccf5e67e38 100644
--- a/kernel/isolation.c
+++ b/kernel/isolation.c
@@ -43,8 +43,14 @@ int __init task_isolation_init(void)
 {
        /* For offstack cpumask, ensure we allocate an empty cpumask early. */
        if (!saw_boot_arg) {
+#ifdef CONFIG_TASK_ISOLATION_ALL
+               alloc_cpumask_var(&task_isolation_map, GFP_KERNEL);
+               cpumask_copy(task_isolation_map, cpu_possible_mask);
+               cpumask_clear_cpu(smp_processor_id(), task_isolation_map);
+#else
                zalloc_cpumask_var(&task_isolation_map, GFP_KERNEL);
                return 0;
+#endif
        }
 
        /*
-- 
2.7.2

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