qemu: conditionally active task isolation

If task isolation is configured, active it on the CPU execution loop.

Higher level management software is supposed to configure task isolation.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/cpus-common.c b/cpus-common.c
index 6e73d3e58d..b394bf0bd7 100644
--- a/cpus-common.c
+++ b/cpus-common.c
@@ -225,9 +225,11 @@ void end_exclusive(void)
     qemu_mutex_unlock(&qemu_cpu_list_lock);
 }
 
-/* Wait for exclusive ops to finish, and begin cpu execution.  */
 void cpu_exec_start(CPUState *cpu)
 {
+    qemu_activate_task_isolation();
+
+    /* Wait for exclusive ops to finish, and begin cpu execution.  */
     qatomic_set(&cpu->running, true);
 
     /* Write cpu->running before reading pending_cpus.  */
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index ba15be9c56..649154d11c 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -686,6 +686,14 @@ char *qemu_get_host_name(Error **errp);
  */
 size_t qemu_get_host_physmem(void);
 
+/**
+ * qemu_activate_task_isolation:
+ *
+ * Enable task isolation, if available, before executing the CPU.
+ *
+ */
+int qemu_activate_task_isolation(void);
+
 /*
  * Toggle write/execute on the pages marked MAP_JIT
  * for the current thread.
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 36820fec16..54cc66c786 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -43,6 +43,8 @@
 
 #ifdef CONFIG_LINUX
 #include <sys/syscall.h>
+#include <sys/prctl.h>
+#include <linux/types.h>
 #endif
 
 #ifdef __FreeBSD__
@@ -866,3 +868,24 @@ size_t qemu_get_host_physmem(void)
 #endif
     return 0;
 }
+
+int qemu_activate_task_isolation(void)
+{
+#if defined(__linux__)
+#ifdef PR_ISOL_CFG_GET
+    unsigned long long fmask;
+
+    ret = prctl(PR_ISOL_CFG_GET, I_CFG_FEAT, 0, &fmask, 0);
+
+    if (ret != -1 && fmask != 0) {
+        ret = prctl(PR_ISOL_ACTIVATE_SET, &fmask, 0, 0, 0);
+        if (ret == -1) {
+            perror("prctl PR_ISOL_ACTIVATE_SET");
+            return ret;
+        }
+    }
+    return ret;
+#endif
+#endif
+	return 0;
+}
diff --git a/util/oslib-win32.c b/util/oslib-win32.c
index f68b8012bb..1c684d82c7 100644
--- a/util/oslib-win32.c
+++ b/util/oslib-win32.c
@@ -842,3 +842,8 @@ size_t qemu_get_host_physmem(void)
     }
     return 0;
 }
+
+int qemu_activate_task_isolation(void)
+{
+    return 0;
+}