Re: [Qemu-devel] [PATCH v4 12/24] linux-user: Initialize pseudo-random seeds for all guest cpus

[Laurent Vivier]

On 06/05/2019 19:33, 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 during clone; which is a no-op unless the
> subsystem is in deterministic mode.
>
> Cc: Laurent Vivier <address@hidden>
> Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>   linux-user/main.c    | 21 ++++++++++-----------
>   linux-user/syscall.c |  3 +++
>   2 files changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/linux-user/main.c b/linux-user/main.c
> index 3d2230320b..7dfb202e5d 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -34,6 +34,7 @@
>   #include "tcg.h"
>   #include "qemu/timer.h"
>   #include "qemu/envlist.h"
> +#include "qemu/guest-random.h"
>   #include "elf.h"
>   #include "trace/control.h"
>   #include "target_elf.h"
> @@ -48,6 +49,7 @@ static int gdbstub_port;
>   static envlist_t *envlist;
>   static const char *cpu_model;
>   static const char *cpu_type;
> +static const char *seed_optarg;
>   unsigned long mmap_min_addr;
>   unsigned long guest_base;
>   int have_guest_base;
> @@ -290,15 +292,9 @@ static void handle_arg_pagesize(const char *arg)
>       }
>   }
>   
> -static void handle_arg_randseed(const char *arg)
> +static void handle_arg_seed(const char *arg)
>   {
> -    unsigned long long seed;
> -
> -    if (parse_uint_full(arg, &seed, 0) != 0 || seed > UINT_MAX) {
> -        fprintf(stderr, "Invalid seed number: %s\n", arg);
> -        exit(EXIT_FAILURE);
> -    }
> -    srand(seed);

It's a detail, but I think you can't remove this srand() in this patch: 
you initialize qemu_guest_random() sequence but the code continues to 
use rand() to have a random number, so the seed value is in fact 
ignored. you can remove it in PATCH 16.

Thanks,
Laurent