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

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 0424c178305845178a5c998f7f6c56e6f54e6fb2..184628ce5645837a190dfb7ca47eaac62f341b53 100644 (file)
--- 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.

diff --git a/include/hw/arm/boot.h b/include/hw/arm/boot.h
index 0bcb58babbad159f63c4e70b8d1c2e4a5a968090..0cfc1c95c4ed184e70bc1b527c32786d6e93fc64 100644 (file)
--- a/include/hw/arm/boot.h
+++ b/include/hw/arm/boot.h
@@ -70,6 +70,9 @@ struct arm_boot_info {
      * boot loader/boot ROM code, and secondary_cpu_reset_hook() should
      * perform any necessary CPU reset handling and set the PC for the
      * secondary CPUs to point at this boot blob.
+     *
+     * These hooks won't be called if secondary CPUs are booting via
+     * emulated PSCI (see psci_conduit below).
      */
     void (*write_secondary_boot)(ARMCPU *cpu,
                                  const struct arm_boot_info *info);