Implement XEN_SYSCTL_CPU_HOTPLUG_{ONLINE,OFFLINE} calls to allow for
enabling/disabling CPU cores in runtime.

Signed-off-by: Mykyta Poturai <mykyta_poturai@epam.com>

v1->v2:
* remove SMT ops
* remove cpu == 0 checks
* add XSM hooks
* only implement for 64bit Arm
---
 xen/arch/arm/sysctl.c | 45 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/xen/arch/arm/sysctl.c b/xen/arch/arm/sysctl.c
index 32cab4feff..fecd649db1 100644
--- a/xen/arch/arm/sysctl.c
+++ b/xen/arch/arm/sysctl.c
@@ -12,6 +12,8 @@
 #include <xen/dt-overlay.h>
 #include <xen/errno.h>
 #include <xen/hypercall.h>
+#include <xen/cpu.h>
+#include <xsm/xsm.h>
 #include <asm/arm64/sve.h>
 #include <public/sysctl.h>
 
@@ -23,6 +25,42 @@ void arch_do_physinfo(struct xen_sysctl_physinfo *pi)
                                        XEN_SYSCTL_PHYSCAP_ARM_SVE_MASK);
 }
 
+#ifdef CONFIG_ARM_64
+static long cpu_up_helper(void *data)
+{
+    unsigned long cpu = (unsigned long) data;
+    return cpu_up(cpu);
+}
+
+static long cpu_down_helper(void *data)
+{
+    unsigned long cpu = (unsigned long) data;
+    return cpu_down(cpu);
+}
+
+static long cpu_hotplug_sysctl(struct xen_sysctl_cpu_hotplug *hotplug)
+{
+    int ret;
+
+    switch (hotplug->op) {
+        case XEN_SYSCTL_CPU_HOTPLUG_ONLINE:
+            ret = xsm_resource_plug_core(XSM_HOOK);
+            if ( ret )
+                return ret;
+            return continue_hypercall_on_cpu(0, cpu_up_helper, _p(hotplug->cpu));
+
+        case XEN_SYSCTL_CPU_HOTPLUG_OFFLINE:
+            ret = xsm_resource_unplug_core(XSM_HOOK);
+            if ( ret )
+                return ret;
+            return continue_hypercall_on_cpu(0, cpu_down_helper, _p(hotplug->cpu));
+
+        default:
+            return -EOPNOTSUPP;
+    }
+}
+#endif
+
 long arch_do_sysctl(struct xen_sysctl *sysctl,
                     XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) u_sysctl)
 {
@@ -34,6 +72,13 @@ long arch_do_sysctl(struct xen_sysctl *sysctl,
         ret = dt_overlay_sysctl(&sysctl->u.dt_overlay);
         break;
 
+/* CPU Hotplug only implemented for 64-bit Arm */
+#ifdef CONFIG_ARM_64
+    case XEN_SYSCTL_cpu_hotplug:
+        ret = cpu_hotplug_sysctl(&sysctl->u.cpu_hotplug);
+        break;
+#endif
+
     default:
         ret = -ENOSYS;
         break;
-- 
2.34.1