KVM: mark vcpu->pid pointer as rcu protected

We do use rcu to protect the pid pointer. Mark it as such and
adopt all code to use the proper access methods.

This was detected by sparse.
"virt/kvm/kvm_main.c:2248:15: error: incompatible types in comparison
expression (different address spaces)"

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 0b50e7b35ed4135f81a3332331132aa0b1fc1c18..bcd37b855c66763995d85e5f9ca80f48b3b1a8e4 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -234,7 +234,7 @@ struct kvm_vcpu {
 
        int guest_fpu_loaded, guest_xcr0_loaded;
        struct swait_queue_head wq;
-       struct pid *pid;
+       struct pid __rcu *pid;
        int sigset_active;
        sigset_t sigset;
        struct kvm_vcpu_stat stat;

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 19f0ecb9b93e23501af3f5c21e2c971cebfd3c6a..fc2d58312fd521f6bbcd49e2dbe86569d1569615 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -293,7 +293,12 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_init);
 
 void kvm_vcpu_uninit(struct kvm_vcpu *vcpu)
 {
-       put_pid(vcpu->pid);
+       /*
+        * no need for rcu_read_lock as VCPU_RUN is the only place that
+        * will change the vcpu->pid pointer and on uninit all file
+        * descriptors are already gone.
+        */
+       put_pid(rcu_dereference_protected(vcpu->pid, 1));
        kvm_arch_vcpu_uninit(vcpu);
        free_page((unsigned long)vcpu->run);
 }
@@ -2551,13 +2556,14 @@ static long kvm_vcpu_ioctl(struct file *filp,
        if (r)
                return r;
        switch (ioctl) {
-       case KVM_RUN:
+       case KVM_RUN: {
+               struct pid *oldpid;
                r = -EINVAL;
                if (arg)
                        goto out;
-               if (unlikely(vcpu->pid != current->pids[PIDTYPE_PID].pid)) {
+               oldpid = rcu_access_pointer(vcpu->pid);
+               if (unlikely(oldpid != current->pids[PIDTYPE_PID].pid)) {
                        /* The thread running this VCPU changed. */
-                       struct pid *oldpid = vcpu->pid;
                        struct pid *newpid = get_task_pid(current, PIDTYPE_PID);
 
                        rcu_assign_pointer(vcpu->pid, newpid);
@@ -2568,6 +2574,7 @@ static long kvm_vcpu_ioctl(struct file *filp,
                r = kvm_arch_vcpu_ioctl_run(vcpu, vcpu->run);
                trace_kvm_userspace_exit(vcpu->run->exit_reason, r);
                break;
+       }
        case KVM_GET_REGS: {
                struct kvm_regs *kvm_regs;