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>
---
Changes v1->v2:
- This is rebased on top of your "or1k-virt-2" branch.
- It makes the change to the new "virt" platform, since that's where it
  makes most sense to have.

 hw/openrisc/virt.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/openrisc/virt.c b/hw/openrisc/virt.c
index 13b0a1d7dc..f1d62fcb7d 100644
--- a/hw/openrisc/virt.c
+++ b/hw/openrisc/virt.c
@@ -19,6 +19,7 @@
 
 #include "qemu/osdep.h"
 #include "qemu/error-report.h"
+#include "qemu/guest-random.h"
 #include "qapi/error.h"
 #include "cpu.h"
 #include "exec/address-spaces.h"
@@ -141,6 +142,7 @@ static void openrisc_create_fdt(OR1KVirtState *state,
     void *fdt;
     int cpu;
     char *nodename;
+    uint8_t rng_seed[32];
 
     fdt = state->fdt = create_device_tree(&state->fdt_size);
     if (!fdt) {
@@ -197,6 +199,10 @@ static void openrisc_create_fdt(OR1KVirtState *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");
 }
-- 
2.35.1

On Wed, Jun 22, 2022 at 01:45:13PM +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>
> ---
> Changes v1->v2:
> - This is rebased on top of your "or1k-virt-2" branch.
> - It makes the change to the new "virt" platform, since that's where it
>   makes most sense to have.

Thanks I have placed this on my or1k-virt-2 branch.

-Stafford