Re: [PATCH] hw/openrisc: pass random seed to fdt

[Stafford Horne]

On Sun, Jun 12, 2022 at 11:59:49PM +0200, Jason A. Donenfeld wrote:
> If the FDT contains /chosen/rng-seed, then the Linux RNG will use it to
> initialize early. Set this using the usual guest random number
> generation function. This is confirmed to successfully initialize the
> RNG on Linux 5.19-rc2.
>
> Cc: Stafford Horne <shorne@gmail.com>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
>  hw/openrisc/openrisc_sim.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/hw/openrisc/openrisc_sim.c b/hw/openrisc/openrisc_sim.c
> index 35adce17ac..41821b5f30 100644
> --- a/hw/openrisc/openrisc_sim.c
> +++ b/hw/openrisc/openrisc_sim.c
> @@ -20,6 +20,7 @@
>  
>  #include "qemu/osdep.h"
>  #include "qemu/error-report.h"
> +#include "qemu/guest-random.h"
>  #include "qapi/error.h"
>  #include "cpu.h"
>  #include "hw/irq.h"
> @@ -115,6 +116,7 @@ static void openrisc_create_fdt(Or1ksimState *state,
>      int cpu;
>      char *nodename;
>      int pic_ph;
> +    uint8_t rng_seed[32];
>  
>      fdt = state->fdt = create_device_tree(&state->fdt_size);
>      if (!fdt) {
> @@ -165,6 +167,10 @@ static void openrisc_create_fdt(Or1ksimState *state,
>          qemu_fdt_setprop_string(fdt, "/chosen", "bootargs", cmdline);
>      }
>  
> +    /* Pass seed to RNG. */
> +    qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
> +    qemu_fdt_setprop(fdt, "/chosen", "rng-seed", rng_seed, sizeof(rng_seed));
> +
>      /* Create aliases node for use by devices. */
>      qemu_fdt_add_subnode(fdt, "/aliases");
>  }

This all looks fine to me.  I will queue it with my current changes.  Since this
is only applying to openrisc_sim I would like to also apply it to virt.  To do
that I need to have a common core openrisc system creation api.  That way I
don't end up copying and pasting this to every platform.

-Stafford