spapr: Don't hijack current_machine->boot_order

QEMU 6.0 moved all the -boot variables to the machine. Especially, the
removal of the boot_order static changed the handling of '-boot once'
from:

    if (boot_once) {
        qemu_boot_set(boot_once, &error_fatal);
        qemu_register_reset(restore_boot_order, g_strdup(boot_order));
    }

to

    if (current_machine->boot_once) {
        qemu_boot_set(current_machine->boot_once, &error_fatal);
        qemu_register_reset(restore_boot_order,
                            g_strdup(current_machine->boot_order));
    }

This means that we now register as subsequent boot order a copy
of current_machine->boot_once that was just set with the previous
call to qemu_boot_set(), i.e. we never transition away from the
once boot order.

It is certainly fragile^Wwrong for the spapr code to hijack a
field of the base machine type object like that. The boot order
rework simply turned this software boundary violation into an
actual bug.

Have the spapr code to handle that with its own field in
SpaprMachineState. Also kfree() the initial boot device
string when "once" was used.

Fixes: 4b7acd2ac821 ("vl: clean up -boot variables")
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1960119
Cc: pbonzini@redhat.com
Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <20210521160735.1901914-1-groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index c23bcc44907102c048364fdba47ef2a02ad84865..4dd90b75cc5285d60995a5b8b79502a46a0a5deb 100644 (file)
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1005,7 +1005,7 @@ static void spapr_dt_chosen(SpaprMachineState *spapr, void *fdt, bool reset)
     _FDT(chosen = fdt_add_subnode(fdt, 0, "chosen"));
 
     if (reset) {
-        const char *boot_device = machine->boot_order;
+        const char *boot_device = spapr->boot_device;
         char *stdout_path = spapr_vio_stdout_path(spapr->vio_bus);
         size_t cb = 0;
         char *bootlist = get_boot_devices_list(&cb);
@@ -2376,8 +2376,10 @@ static SaveVMHandlers savevm_htab_handlers = {
 static void spapr_boot_set(void *opaque, const char *boot_device,
                            Error **errp)
 {
-    MachineState *machine = MACHINE(opaque);
-    machine->boot_order = g_strdup(boot_device);
+    SpaprMachineState *spapr = SPAPR_MACHINE(opaque);
+
+    g_free(spapr->boot_device);
+    spapr->boot_device = g_strdup(boot_device);
 }
 
 static void spapr_create_lmb_dr_connectors(SpaprMachineState *spapr)

diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index bbf817af4647d26fed2c6f959063f151a7e74475..f05219f75ef6c9757d33c7bb92160ca2d3fcab79 100644 (file)
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -223,6 +223,9 @@ struct SpaprMachineState {
     int fwnmi_machine_check_interlock;
     QemuCond fwnmi_machine_check_interlock_cond;
 
+    /* Set by -boot */
+    char *boot_device;
+
     /*< public >*/
     char *kvm_type;
     char *host_model;