diff options
| -rw-r--r-- | arch/arm64/include/asm/kvm_host.h | 2 | ||||
| -rw-r--r-- | include/linux/kvm_host.h | 3 | ||||
| -rw-r--r-- | virt/kvm/kvm_main.c | 39 |
3 files changed, 28 insertions, 16 deletions
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index bf64fed9820e..04febe60c88e 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -1140,7 +1140,7 @@ int __kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu, void kvm_arm_halt_guest(struct kvm *kvm); void kvm_arm_resume_guest(struct kvm *kvm); -#define vcpu_has_run_once(vcpu) !!rcu_access_pointer((vcpu)->pid) +#define vcpu_has_run_once(vcpu) (!!READ_ONCE((vcpu)->pid)) #ifndef __KVM_NVHE_HYPERVISOR__ #define kvm_call_hyp_nvhe(f, ...) \ diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 02f0206fd2dc..18a1672ffcbf 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -334,7 +334,8 @@ struct kvm_vcpu { #ifndef __KVM_HAVE_ARCH_WQP struct rcuwait wait; #endif - struct pid __rcu *pid; + struct pid *pid; + rwlock_t pid_lock; int sigset_active; sigset_t sigset; unsigned int halt_poll_ns; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 17048d9575e3..c1876b9ed213 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -447,6 +447,7 @@ static void kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id) vcpu->kvm = kvm; vcpu->vcpu_id = id; vcpu->pid = NULL; + rwlock_init(&vcpu->pid_lock); #ifndef __KVM_HAVE_ARCH_WQP rcuwait_init(&vcpu->wait); #endif @@ -474,7 +475,7 @@ static void kvm_vcpu_destroy(struct kvm_vcpu *vcpu) * the vcpu->pid pointer, and at destruction time all file descriptors * are already gone. */ - put_pid(rcu_dereference_protected(vcpu->pid, 1)); + put_pid(vcpu->pid); free_page((unsigned long)vcpu->run); kmem_cache_free(kvm_vcpu_cache, vcpu); @@ -3770,15 +3771,17 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_kick); int kvm_vcpu_yield_to(struct kvm_vcpu *target) { - struct pid *pid; struct task_struct *task = NULL; int ret; - rcu_read_lock(); - pid = rcu_dereference(target->pid); - if (pid) - task = get_pid_task(pid, PIDTYPE_PID); - rcu_read_unlock(); + if (!read_trylock(&target->pid_lock)) + return 0; + + if (target->pid) + task = get_pid_task(target->pid, PIDTYPE_PID); + + read_unlock(&target->pid_lock); + if (!task) return 0; ret = yield_to(task, 1); @@ -4030,9 +4033,9 @@ static int vcpu_get_pid(void *data, u64 *val) { struct kvm_vcpu *vcpu = data; - rcu_read_lock(); - *val = pid_nr(rcu_dereference(vcpu->pid)); - rcu_read_unlock(); + read_lock(&vcpu->pid_lock); + *val = pid_nr(vcpu->pid); + read_unlock(&vcpu->pid_lock); return 0; } @@ -4318,7 +4321,14 @@ static long kvm_vcpu_ioctl(struct file *filp, r = -EINVAL; if (arg) goto out; - oldpid = rcu_access_pointer(vcpu->pid); + + /* + * Note, vcpu->pid is primarily protected by vcpu->mutex. The + * dedicated r/w lock allows other tasks, e.g. other vCPUs, to + * read vcpu->pid while this vCPU is in KVM_RUN, e.g. to yield + * directly to this vCPU + */ + oldpid = vcpu->pid; if (unlikely(oldpid != task_pid(current))) { /* The thread running this VCPU changed. */ struct pid *newpid; @@ -4328,9 +4338,10 @@ static long kvm_vcpu_ioctl(struct file *filp, break; newpid = get_task_pid(current, PIDTYPE_PID); - rcu_assign_pointer(vcpu->pid, newpid); - if (oldpid) - synchronize_rcu(); + write_lock(&vcpu->pid_lock); + vcpu->pid = newpid; + write_unlock(&vcpu->pid_lock); + put_pid(oldpid); } vcpu->wants_to_run = !READ_ONCE(vcpu->run->immediate_exit__unsafe); |