[RFC,1/3] KVM: keep track of running ioctls

Commit Message

Emanuele Giuseppe Esposito Nov. 4, 2022, 3:14 p.m. UTC

kvm_in_ioctl_lock uses a QemuLockCnt to keep track of the running
ioctls. It will be used by the memory listener to make sure no
new ioctl runs when it has to perform memslots modifications.

Signed-off-by: David Hildenbrand <[e-mail]>
Signed-off-by: Emanuele Giuseppe Esposito <[e-mail]>
---
 accel/kvm/kvm-all.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

Patch

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index f99b0becd8..099d7bda56 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -105,6 +105,8 @@  static int kvm_sstep_flags;
 static bool kvm_immediate_exit;
 static hwaddr kvm_max_slot_size = ~0;
 
+QemuLockCnt kvm_in_ioctl_lock;
+
 static const KVMCapabilityInfo kvm_required_capabilites[] = {
     KVM_CAP_INFO(USER_MEMORY),
     KVM_CAP_INFO(DESTROY_MEMORY_REGION_WORKS),
@@ -2310,6 +2312,7 @@  static int kvm_init(MachineState *ms)
     assert(TARGET_PAGE_SIZE <= qemu_real_host_page_size());
 
     s->sigmask_len = 8;
+    qemu_lockcnt_init(&kvm_in_ioctl_lock);
 
 #ifdef KVM_CAP_SET_GUEST_DEBUG
     QTAILQ_INIT(&s->kvm_sw_breakpoints);
@@ -2808,6 +2811,18 @@  static void kvm_eat_signals(CPUState *cpu)
     } while (sigismember(&chkset, SIG_IPI));
 }
 
+static void kvm_set_in_ioctl(bool in_ioctl)
+{
+    if (likely(qemu_mutex_iothread_locked())) {
+        return;
+    }
+    if (in_ioctl) {
+        qemu_lockcnt_inc(&kvm_in_ioctl_lock);
+    } else {
+        qemu_lockcnt_dec(&kvm_in_ioctl_lock);
+    }
+}
+
 int kvm_cpu_exec(CPUState *cpu)
 {
     struct kvm_run *run = cpu->kvm_run;
@@ -3014,7 +3029,9 @@  int kvm_vm_ioctl(KVMState *s, int type, ...)
     va_end(ap);
 
     trace_kvm_vm_ioctl(type, arg);
+    kvm_set_in_ioctl(true);
     ret = ioctl(s->vmfd, type, arg);
+    kvm_set_in_ioctl(false);
     if (ret == -1) {
         ret = -errno;
     }
@@ -3050,7 +3067,9 @@  int kvm_device_ioctl(int fd, int type, ...)
     va_end(ap);
 
     trace_kvm_device_ioctl(fd, type, arg);
+    kvm_set_in_ioctl(true);
     ret = ioctl(fd, type, arg);
+    kvm_set_in_ioctl(false);
     if (ret == -1) {
         ret = -errno;
     }