Re: [PULL 7/9] hw/guest-loader: pass random seed to fdt

["Alex Bennée" <alex.bennee@linaro.org>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> From: "Jason A. Donenfeld" <Jason@zx2c4.com>
>
> 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 FDT node is part of the DT specification.
>
> Cc: Alex Bennée <alex.bennee@linaro.org>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> Message-Id: <20220719121559.135355-1-Jason@zx2c4.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  hw/core/guest-loader.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/hw/core/guest-loader.c b/hw/core/guest-loader.c
> index 391c875a29..4f8572693c 100644
> --- a/hw/core/guest-loader.c
> +++ b/hw/core/guest-loader.c
> @@ -31,6 +31,7 @@
>  #include "hw/qdev-properties.h"
>  #include "qapi/error.h"
>  #include "qemu/module.h"
> +#include "qemu/guest-random.h"
>  #include "guest-loader.h"
>  #include "sysemu/device_tree.h"
>  #include "hw/boards.h"
> @@ -46,6 +47,7 @@ static void loader_insert_platform_data(GuestLoaderState *s, int size,
>      g_autofree char *node = g_strdup_printf("/chosen/module@0x%08" PRIx64,
>                                              s->addr);
>      uint64_t reg_attr[2] = {cpu_to_be64(s->addr), cpu_to_be64(size)};
> +    uint8_t rng_seed[32];
>  
>      if (!fdt) {
>          error_setg(errp, "Cannot modify FDT fields if the machine has none");
> @@ -55,6 +57,9 @@ static void loader_insert_platform_data(GuestLoaderState *s, int size,
>      qemu_fdt_add_subnode(fdt, node);
>      qemu_fdt_setprop(fdt, node, "reg", &reg_attr, sizeof(reg_attr));
>  
> +    qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
> +    qemu_fdt_setprop(fdt, node, "rng-seed", rng_seed, sizeof(rng_seed));
> +

Why are we inserting this here? The guest-loader is only building on
what the machine type has already constructed which in the case of -M
virt for riscv and ARM already has code for this.

>      if (s->kernel) {
>          const char *compat[2] = { "multiboot,module", "multiboot,kernel" };
>          if (qemu_fdt_setprop_string_array(fdt, node, "compatible",


-- 
Alex Bennée