Due to the way how CPU 0 is offlined on x86, we cannot "steal" it from
the root cell and give it to a different owner. Catch any configuration
that tries to do so and reject this attempt.
Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
---
driver/cell.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/driver/cell.c b/driver/cell.c
index 67edb732..23839812 100644
--- a/driver/cell.c
+++ b/driver/cell.c
@@ -220,6 +220,19 @@ int jailhouse_cmd_cell_create(struct jailhouse_cell_create
__user *arg)
/* Off-line each CPU assigned to the new cell and remove it from the
* root cell's set. */
for_each_cpu(cpu, &cell->cpus_assigned) {
+#ifdef CONFIG_X86
+ if (cpu == 0) {
+ /*
+ * On x86, Linux only parks CPU 0 when offlining it and
+ * expects to be able to get it back by sending an IPI.
+ * This is not support by Jailhouse wich destroys the
+ * CPU state across non-root assignments.
+ */
+ pr_err("Cannot assign CPU 0 to other cells\n");
+ err = -EINVAL;
+ goto error_cpu_online;
+ }
+#endif
if (cpu_online(cpu)) {
err = cpu_down(cpu);
if (err)
--
2.16.4
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