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| author | Christian Borntraeger <borntraeger@de.ibm.com> | 2014-08-05 16:44:14 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2014-12-04 15:29:13 +0100 |
| commit | 7a72f7a140bfd3a5dae73088947010bfdbcf6a40 (patch) | |
| tree | bb6f945f4460a39e7d0e6b242ecf656508891c27 /virt | |
| parent | KVM: don't check for PF_VCPU when yielding (diff) | |
| download | linux-7a72f7a140bfd3a5dae73088947010bfdbcf6a40.tar.xz linux-7a72f7a140bfd3a5dae73088947010bfdbcf6a40.zip | |
KVM: track pid for VCPU only on KVM_RUN ioctl
We currently track the pid of the task that runs the VCPU in vcpu_load.
If a yield to that VCPU is triggered while the PID of the wrong thread
is active, the wrong thread might receive a yield, but this will most
likely not help the executing thread at all. Instead, if we only track
the pid on the KVM_RUN ioctl, there are two possibilities:
1) the thread that did a non-KVM_RUN ioctl is holding a mutex that
the VCPU thread is waiting for. In this case, the VCPU thread is not
runnable, but we also do not do a wrong yield.
2) the thread that did a non-KVM_RUN ioctl is sleeping, or doing
something that does not block the VCPU thread. In this case, the
VCPU thread can receive the directed yield correctly.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
CC: Rik van Riel <riel@redhat.com>
CC: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
CC: Michael Mueller <mimu@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
| -rw-r--r-- | virt/kvm/kvm_main.c | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 2ffee3018a3d..c5c186af823b 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -124,15 +124,6 @@ int vcpu_load(struct kvm_vcpu *vcpu) if (mutex_lock_killable(&vcpu->mutex)) return -EINTR; - if (unlikely(vcpu->pid != 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); - if (oldpid) - synchronize_rcu(); - put_pid(oldpid); - } cpu = get_cpu(); preempt_notifier_register(&vcpu->preempt_notifier); kvm_arch_vcpu_load(vcpu, cpu); @@ -2050,6 +2041,15 @@ static long kvm_vcpu_ioctl(struct file *filp, r = -EINVAL; if (arg) goto out; + if (unlikely(vcpu->pid != 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); + if (oldpid) + synchronize_rcu(); + put_pid(oldpid); + } r = kvm_arch_vcpu_ioctl_run(vcpu, vcpu->run); trace_kvm_userspace_exit(vcpu->run->exit_reason, r); break; |