[PATCH kvmtool v3 08/17] Add helpers to pause the VM from vCPU thread

[Oliver Upton <oliver.upton@linux.dev>]

Pausing the VM from a vCPU thread is perilous with the current helpers,
as it waits indefinitely for a signal that never comes when invoked from
a vCPU thread. Instead, add a helper for pausing the VM from a vCPU,
working around the issue by explicitly marking the caller as paused
before proceeding.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 include/kvm/kvm-cpu.h |  3 +++
 kvm-cpu.c             | 16 ++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/include/kvm/kvm-cpu.h b/include/kvm/kvm-cpu.h
index 0f16f8d6e872..9a4901bf94ca 100644
--- a/include/kvm/kvm-cpu.h
+++ b/include/kvm/kvm-cpu.h
@@ -29,4 +29,7 @@ void kvm_cpu__show_page_tables(struct kvm_cpu *vcpu);
 void kvm_cpu__arch_nmi(struct kvm_cpu *cpu);
 void kvm_cpu__run_on_all_cpus(struct kvm *kvm, struct kvm_cpu_task *task);
 
+void kvm_cpu__pause_vm(struct kvm_cpu *vcpu);
+void kvm_cpu__continue_vm(struct kvm_cpu *vcpu);
+
 #endif /* KVM__KVM_CPU_H */
diff --git a/kvm-cpu.c b/kvm-cpu.c
index 1c566b3f21d6..9adc9d4f7841 100644
--- a/kvm-cpu.c
+++ b/kvm-cpu.c
@@ -141,6 +141,22 @@ void kvm_cpu__run_on_all_cpus(struct kvm *kvm, struct kvm_cpu_task *task)
 	mutex_unlock(&task_lock);
 }
 
+void kvm_cpu__pause_vm(struct kvm_cpu *vcpu)
+{
+	/*
+	 * Mark the calling vCPU as paused to avoid waiting indefinitely for a
+	 * signal exit.
+	 */
+	vcpu->paused = true;
+	kvm__pause(vcpu->kvm);
+}
+
+void kvm_cpu__continue_vm(struct kvm_cpu *vcpu)
+{
+	vcpu->paused = false;
+	kvm__continue(vcpu->kvm);
+}
+
 int kvm_cpu__start(struct kvm_cpu *cpu)
 {
 	sigset_t sigset;
-- 
2.41.0.585.gd2178a4bd4-goog