hw/riscv: virt: pass random seed to fdt

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: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Message-Id: <20220613115810.178210-1-Jason@zx2c4.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index bc424dd..f2ce566 100644 (file)
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -21,6 +21,7 @@
 #include "qemu/osdep.h"
 #include "qemu/units.h"
 #include "qemu/error-report.h"
+#include "qemu/guest-random.h"
 #include "qapi/error.h"
 #include "hw/boards.h"
 #include "hw/loader.h"
@@ -998,6 +999,7 @@ static void create_fdt(RISCVVirtState *s, const MemMapEntry *memmap,
     MachineState *mc = MACHINE(s);
     uint32_t phandle = 1, irq_mmio_phandle = 1, msi_pcie_phandle = 1;
     uint32_t irq_pcie_phandle = 1, irq_virtio_phandle = 1;
+    uint8_t rng_seed[32];
 
     if (mc->dtb) {
         mc->fdt = load_device_tree(mc->dtb, &s->fdt_size);
@@ -1046,6 +1048,10 @@ update_bootargs:
     if (cmdline && *cmdline) {
         qemu_fdt_setprop_string(mc->fdt, "/chosen", "bootargs", cmdline);
     }
+
+    /* Pass seed to RNG */
+    qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
+    qemu_fdt_setprop(mc->fdt, "/chosen", "rng-seed", rng_seed, sizeof(rng_seed));
 }
 
 static inline DeviceState *gpex_pcie_init(MemoryRegion *sys_mem,