accel/mshv: implement cpu_thread_is_idle() hook

In MSHV the hypervisor APIC is always used, so we to implement this hook
to make sure the AP's vcpu thread is not blocked waiting for an INIT SIPI
by the BSP. Without this change soft reboots with -smp cpus>=2 will
hang.

Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
Reviewed-by: Mohamed Mediouni <mohamed@unpredictable.fr>
Link: https://lore.kernel.org/r/20260421-mshv_accel_arm64_supp-v3-9-469f544778ba@linux.microsoft.com
[Make comment not x86 specific. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/accel/mshv/mshv-all.c b/accel/mshv/mshv-all.c
index 58af674bd9931c1319c8a2b29b740a74cf31c324..58d8638c0c1cb62afda2b16af2633f643c597495 100644 (file)
--- a/accel/mshv/mshv-all.c
+++ b/accel/mshv/mshv-all.c
@@ -714,11 +714,23 @@ static const TypeInfo mshv_accel_type = {
     .instance_size = sizeof(MshvState),
 };
 
+/*
+ * MSHV manages secondary processors in the hypervisor. SIPI for x86 and
+ * PSCI for Arm are handled internally. Halted vCPUs must still enter
+ * mshv_cpu_exec() so that MSHV_RUN_VP is called and the hypervisor will
+ * wake APs.
+ */
+static bool mshv_vcpu_thread_is_idle(CPUState *cpu)
+{
+    return false;
+}
+
 static void mshv_accel_ops_class_init(ObjectClass *oc, const void *data)
 {
     AccelOpsClass *ops = ACCEL_OPS_CLASS(oc);
 
     ops->create_vcpu_thread = mshv_start_vcpu_thread;
+    ops->cpu_thread_is_idle = mshv_vcpu_thread_is_idle;
     ops->synchronize_post_init = mshv_cpu_synchronize_post_init;
     ops->synchronize_post_reset = mshv_cpu_synchronize_post_reset;
     ops->synchronize_state = mshv_cpu_synchronize;