Re: [Qemu-devel] [PATCH v3 10/23] cpus: Initialize pseudo-random seeds for all guest cpus

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 3/15/19 4:26 AM, Richard Henderson wrote:
> 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.
> 
> Cc: Daniel P. Berrangé <berrange@redhat.com>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/qom/cpu.h |  1 +
>  cpus.c            |  9 +++++++++
>  vl.c              |  4 ++++
>  qemu-options.hx   | 10 ++++++++++
>  4 files changed, 24 insertions(+)
> 
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index 1d6099e5d4..343cc6d51e 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -372,6 +372,7 @@ struct CPUState {
>      int singlestep_enabled;
>      int64_t icount_budget;
>      int64_t icount_extra;
> +    uint64_t random_seed;
>      sigjmp_buf jmp_env;
>  
>      QemuMutex work_mutex;
> diff --git a/cpus.c b/cpus.c
> index e83f72b48b..6d88f6bfcd 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -49,6 +49,7 @@
>  #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"
> @@ -1275,6 +1276,7 @@ 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)) {
> @@ -1318,6 +1320,7 @@ 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();
> @@ -1477,6 +1480,7 @@ 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) {
> @@ -1591,6 +1595,7 @@ 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)) {
> @@ -1630,6 +1635,7 @@ 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)) {
> @@ -1670,6 +1676,7 @@ 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)) {
> @@ -1723,6 +1730,7 @@ 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;
> @@ -2070,6 +2078,7 @@ 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,
> diff --git a/vl.c b/vl.c
> index c1d5484e12..d84f883c2c 100644
> --- a/vl.c
> +++ b/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
>  
> @@ -3330,6 +3331,9 @@ 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;
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 08749a3391..b8da998668 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -3601,6 +3601,16 @@ 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

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> +
>  DEF("L", HAS_ARG, QEMU_OPTION_L, \
>      "-L path         set the directory for the BIOS, VGA BIOS and keymaps\n",
>      QEMU_ARCH_ALL)
>