KVM: make processes waiting on vcpu mutex killable
vcpu mutex can be held for unlimited time so
taking it with mutex_lock on an ioctl is wrong:
one process could be passed a vcpu fd and
call this ioctl on the vcpu used by another process,
it will then be unkillable until the owner exits.
Call mutex_lock_killable instead and return status.
Note: mutex_lock_interruptible would be even nicer,
but I am not sure all users are prepared to handle EINTR
from these ioctls. They might misinterpret it as an error.
Cleanup paths expect a vcpu that can't be used by
any userspace so this will always succeed - catch bugs
by calling BUG_ON.
Catch callers that don't check return state by adding
__must_check.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c4d451e..19047ea 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6016,7 +6016,9 @@
int r;
vcpu->arch.mtrr_state.have_fixed = 1;
- vcpu_load(vcpu);
+ r = vcpu_load(vcpu);
+ if (r)
+ return r;
r = kvm_arch_vcpu_reset(vcpu);
if (r == 0)
r = kvm_mmu_setup(vcpu);
@@ -6027,9 +6029,11 @@
void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
{
+ int r;
vcpu->arch.apf.msr_val = 0;
- vcpu_load(vcpu);
+ r = vcpu_load(vcpu);
+ BUG_ON(r);
kvm_mmu_unload(vcpu);
vcpu_put(vcpu);
@@ -6275,7 +6279,9 @@
static void kvm_unload_vcpu_mmu(struct kvm_vcpu *vcpu)
{
- vcpu_load(vcpu);
+ int r;
+ r = vcpu_load(vcpu);
+ BUG_ON(r);
kvm_mmu_unload(vcpu);
vcpu_put(vcpu);
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 4079193..80bfc88 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -408,7 +408,7 @@
int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id);
void kvm_vcpu_uninit(struct kvm_vcpu *vcpu);
-void vcpu_load(struct kvm_vcpu *vcpu);
+int __must_check vcpu_load(struct kvm_vcpu *vcpu);
void vcpu_put(struct kvm_vcpu *vcpu);
int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4fe02d90..cc3f6dc 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -131,11 +131,12 @@
/*
* Switches to specified vcpu, until a matching vcpu_put()
*/
-void vcpu_load(struct kvm_vcpu *vcpu)
+int vcpu_load(struct kvm_vcpu *vcpu)
{
int cpu;
- mutex_lock(&vcpu->mutex);
+ 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;
@@ -148,6 +149,7 @@
preempt_notifier_register(&vcpu->preempt_notifier);
kvm_arch_vcpu_load(vcpu, cpu);
put_cpu();
+ return 0;
}
void vcpu_put(struct kvm_vcpu *vcpu)
@@ -1891,7 +1893,9 @@
#endif
- vcpu_load(vcpu);
+ r = vcpu_load(vcpu);
+ if (r)
+ return r;
switch (ioctl) {
case KVM_RUN:
r = -EINVAL;
