spapr: Fix record-replay machine reset consuming too many events

spapr_machine_reset gets a random number to populate the device-tree
rng seed with. When loading a snapshot for record-replay, the machine
is reset again, and that tries to consume the random event record
again, crashing due to inconsistent record

Fix this by saving the seed to populate the device tree with, and
skipping the rng on snapshot load.

Acked-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index c0b0ada121f9285fe050de049738319c27dd51a3..f7cc6a890f451d1469b5e8aa01d21a8e08499f28 100644 (file)
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1022,7 +1022,6 @@ static void spapr_dt_chosen(SpaprMachineState *spapr, void *fdt, bool reset)
 {
     MachineState *machine = MACHINE(spapr);
     SpaprMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
-    uint8_t rng_seed[32];
     int chosen;
 
     _FDT(chosen = fdt_add_subnode(fdt, 0, "chosen"));
@@ -1100,8 +1099,7 @@ static void spapr_dt_chosen(SpaprMachineState *spapr, void *fdt, bool reset)
         spapr_dt_ov5_platform_support(spapr, fdt, chosen);
     }
 
-    qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
-    _FDT(fdt_setprop(fdt, chosen, "rng-seed", rng_seed, sizeof(rng_seed)));
+    _FDT(fdt_setprop(fdt, chosen, "rng-seed", spapr->fdt_rng_seed, 32));
 
     _FDT(spapr_dt_ovec(fdt, chosen, spapr->ov5_cas, "ibm,architecture-vec-5"));
 }
@@ -1654,6 +1652,14 @@ static void spapr_machine_reset(MachineState *machine, ShutdownCause reason)
     void *fdt;
     int rc;
 
+    if (reason != SHUTDOWN_CAUSE_SNAPSHOT_LOAD) {
+        /*
+         * Record-replay snapshot load must not consume random, this was
+         * already replayed from initial machine reset.
+         */
+        qemu_guest_getrandom_nofail(spapr->fdt_rng_seed, 32);
+    }
+
     pef_kvm_reset(machine->cgs, &error_fatal);
     spapr_caps_apply(spapr);
 

diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index f47e8419a575b95f1a67ea8f100cecc35027108c..f4bd204d8633696102d66a060e4d85b6b4098206 100644 (file)
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -204,6 +204,7 @@ struct SpaprMachineState {
     uint32_t fdt_size;
     uint32_t fdt_initial_size;
     void *fdt_blob;
+    uint8_t fdt_rng_seed[32];
     long kernel_size;
     bool kernel_le;
     uint64_t kernel_addr;