cpus: Initialize pseudo-random seeds for all guest cpus

When the -seed option is given, call qemu_guest_random_seed_main,
putting the subsystem into deterministic mode.  Pass derived seeds
to each cpu created; which is a no-op unless the subsystem is in
deterministic mode.

Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

cpus.c

@@ -50,6 +50,7 @@
 #include "qemu/option.h"
 #include "qemu/bitmap.h"
 #include "qemu/seqlock.h"
+#include "qemu/guest-random.h"
 #include "tcg.h"
 #include "hw/nmi.h"
 #include "sysemu/replay.h"
@@ -1276,6 +1277,7 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
     /* signal CPU creation */
     cpu->created = true;
     qemu_cond_signal(&qemu_cpu_cond);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     do {
         if (cpu_can_run(cpu)) {
@@ -1319,6 +1321,7 @@ static void *qemu_dummy_cpu_thread_fn(void *arg)
     /* signal CPU creation */
     cpu->created = true;
     qemu_cond_signal(&qemu_cpu_cond);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     do {
         qemu_mutex_unlock_iothread();
@@ -1478,6 +1481,7 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg)
     cpu->created = true;
     cpu->can_do_io = 1;
     qemu_cond_signal(&qemu_cpu_cond);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     /* wait for initial kick-off after machine start */
     while (first_cpu->stopped) {
@@ -1592,6 +1596,7 @@ static void *qemu_hax_cpu_thread_fn(void *arg)
 
     hax_init_vcpu(cpu);
     qemu_cond_signal(&qemu_cpu_cond);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     do {
         if (cpu_can_run(cpu)) {
@@ -1631,6 +1636,7 @@ static void *qemu_hvf_cpu_thread_fn(void *arg)
     /* signal CPU creation */
     cpu->created = true;
     qemu_cond_signal(&qemu_cpu_cond);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     do {
         if (cpu_can_run(cpu)) {
@@ -1671,6 +1677,7 @@ static void *qemu_whpx_cpu_thread_fn(void *arg)
     /* signal CPU creation */
     cpu->created = true;
     qemu_cond_signal(&qemu_cpu_cond);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     do {
         if (cpu_can_run(cpu)) {
@@ -1724,6 +1731,7 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
     cpu->can_do_io = 1;
     current_cpu = cpu;
     qemu_cond_signal(&qemu_cpu_cond);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     /* process any pending work */
     cpu->exit_request = 1;
@@ -2071,6 +2079,7 @@ void qemu_init_vcpu(CPUState *cpu)
     cpu->nr_cores = smp_cores;
     cpu->nr_threads = smp_threads;
     cpu->stopped = true;
+    cpu->random_seed = qemu_guest_random_seed_thread_part1();
 
     if (!cpu->as) {
         /* If the target cpu hasn't set up any address spaces itself,

include/qom/cpu.h

@@ -375,6 +375,7 @@ struct CPUState {
     int singlestep_enabled;
     int64_t icount_budget;
     int64_t icount_extra;
+    uint64_t random_seed;
     sigjmp_buf jmp_env;
 
     QemuMutex work_mutex;

qemu-options.hx

@@ -3641,6 +3641,16 @@ the 0x200 sized block starting at 0xffffffc000080000 and another 0x1000 sized
 block starting at 0xffffffc00005f000.
 ETEXI
 
+DEF("seed", HAS_ARG, QEMU_OPTION_seed, \
+    "-seed number       seed the pseudo-random number generator\n",
+    QEMU_ARCH_ALL)
+STEXI
+@item -seed @var{number}
+@findex -seed
+Force the guest to use a deterministic pseudo-random number generator, seeded
+with @var{number}.  This does not affect crypto routines within the host.
+ETEXI
+
 DEF("L", HAS_ARG, QEMU_OPTION_L, \
     "-L path         set the directory for the BIOS, VGA BIOS and keymaps\n",
     QEMU_ARCH_ALL)

vl.c

@@ -128,6 +128,7 @@ int main(int argc, char **argv)
 #include "qapi/qapi-commands-ui.h"
 #include "qapi/qmp/qerror.h"
 #include "sysemu/iothread.h"
+#include "qemu/guest-random.h"
 
 #define MAX_VIRTIO_CONSOLES 1
 
@@ -3349,6 +3350,9 @@ int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_DFILTER:
                 qemu_set_dfilter_ranges(optarg, &error_fatal);
                 break;
+            case QEMU_OPTION_seed:
+                qemu_guest_random_seed_main(optarg, &error_fatal);
+                break;
             case QEMU_OPTION_s:
                 add_device_config(DEV_GDB, "tcp::" DEFAULT_GDBSTUB_PORT);
                 break;