hw/arm/boot: Don't write secondary boot stub if using PSCI

If we're using PSCI emulation to start secondary CPUs, there is no
point in writing the "secondary boot" stub code, because it will
never be used -- secondary CPUs start powered-off, and when powered
on are set to begin execution at the address specified by the guest's
power-on PSCI call, not at the stub.

Move the call to the hook that writes the secondary boot stub code so
that we can do it only if we're starting a Linux kernel and not using
PSCI.

(None of the users of the hook care about the ordering of its call
relative to anything else: they only use it to write a rom blob to
guest memory.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Tested-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Message-id: 20220127154639.2090164-14-peter.maydell@linaro.org

1 files changed, 24 insertions, 11 deletions

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 0424c17..184628c 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -804,7 +804,7 @@ static void do_cpu_reset(void *opaque)
                         set_kernel_args(info, as);
                     }
                 }
-            } else {
+            } else if (info->secondary_cpu_reset_hook) {
                 info->secondary_cpu_reset_hook(cpu, info);
             }
         }
@@ -1030,13 +1030,6 @@ static void arm_setup_direct_kernel_boot(ARMCPU *cpu,
         elf_machine = EM_ARM;
     }
 
-    if (!info->secondary_cpu_reset_hook) {
-        info->secondary_cpu_reset_hook = default_reset_secondary;
-    }
-    if (!info->write_secondary_boot) {
-        info->write_secondary_boot = default_write_secondary;
-    }
-
     if (info->nb_cpus == 0)
         info->nb_cpus = 1;
 
@@ -1216,9 +1209,6 @@ static void arm_setup_direct_kernel_boot(ARMCPU *cpu,
         write_bootloader("bootloader", info->loader_start,
                          primary_loader, fixupcontext, as);
 
-        if (info->nb_cpus > 1) {
-            info->write_secondary_boot(cpu, info);
-        }
         if (info->write_board_setup) {
             info->write_board_setup(cpu, info);
         }
@@ -1385,6 +1375,29 @@ void arm_load_kernel(ARMCPU *cpu, MachineState *ms, struct arm_boot_info *info)
         }
     }
 
+    if (info->psci_conduit == QEMU_PSCI_CONDUIT_DISABLED &&
+        info->is_linux && info->nb_cpus > 1) {
+        /*
+         * We're booting Linux but not using PSCI, so for SMP we need
+         * to write a custom secondary CPU boot loader stub, and arrange
+         * for the secondary CPU reset to make the accompanying initialization.
+         */
+        if (!info->secondary_cpu_reset_hook) {
+            info->secondary_cpu_reset_hook = default_reset_secondary;
+        }
+        if (!info->write_secondary_boot) {
+            info->write_secondary_boot = default_write_secondary;
+        }
+        info->write_secondary_boot(cpu, info);
+    } else {
+        /*
+         * No secondary boot stub; don't use the reset hook that would
+         * have set the CPU up to call it
+         */
+        info->write_secondary_boot = NULL;
+        info->secondary_cpu_reset_hook = NULL;
+    }
+
     /*
      * arm_load_dtb() may add a PSCI node so it must be called after we have
      * decided whether to enable PSCI and set the psci-conduit CPU properties.