3.16.64-rc1 review patch. If anyone has any objections, please let me know.
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From: Christoffer Dall christoffer.dall@linaro.org
commit a28ebea2adc4a2bef5989a5a181ec238f59fbcad upstream.
KVM devices were manipulating list data structures without any form of synchronization, and some implementations of the create operations also suffered from a lack of synchronization.
Now when we've split the xics create operation into create and init, we can hold the kvm->lock mutex while calling the create operation and when manipulating the devices list.
The error path in the generic code gets slightly ugly because we have to take the mutex again and delete the device from the list, but holding the mutex during anon_inode_getfd or releasing/locking the mutex in the common non-error path seemed wrong.
Signed-off-by: Christoffer Dall christoffer.dall@linaro.org Reviewed-by: Paolo Bonzini pbonzini@redhat.com Acked-by: Christian Borntraeger borntraeger@de.ibm.com Signed-off-by: Radim Krčmář rkrcmar@redhat.com [bwh: Backported to 3.16: - Drop change to a failure path that doesn't exist in kvm_vgic_create() - Adjust filename, context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/arch/arm/kvm/arm.c +++ b/arch/arm/kvm/arm.c @@ -799,10 +799,13 @@ long kvm_arch_vm_ioctl(struct file *filp
switch (ioctl) { case KVM_CREATE_IRQCHIP: { - if (vgic_present) - return kvm_vgic_create(kvm); - else + int ret; + if (!vgic_present) return -ENXIO; + mutex_lock(&kvm->lock); + ret = kvm_vgic_create(kvm); + mutex_unlock(&kvm->lock); + return ret; } case KVM_ARM_SET_DEVICE_ADDR: { struct kvm_arm_device_addr dev_addr; --- a/arch/powerpc/kvm/book3s_xics.c +++ b/arch/powerpc/kvm/book3s_xics.c @@ -1239,12 +1239,10 @@ static int kvmppc_xics_create(struct kvm xics->kvm = kvm;
/* Already there ? */ - mutex_lock(&kvm->lock); if (kvm->arch.xics) ret = -EEXIST; else kvm->arch.xics = xics; - mutex_unlock(&kvm->lock);
if (ret) { kfree(xics); --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1059,6 +1059,12 @@ struct kvm_device { /* create, destroy, and name are mandatory */ struct kvm_device_ops { const char *name; + + /* + * create is called holding kvm->lock and any operations not suitable + * to do while holding the lock should be deferred to init (see + * below). + */ int (*create)(struct kvm_device *dev, u32 type);
/* --- a/virt/kvm/arm/vgic.c +++ b/virt/kvm/arm/vgic.c @@ -1624,12 +1624,8 @@ int kvm_vgic_create(struct kvm *kvm) int i, vcpu_lock_idx = -1, ret; struct kvm_vcpu *vcpu;
- mutex_lock(&kvm->lock); - - if (kvm->arch.vgic.vctrl_base) { - ret = -EEXIST; - goto out; - } + if (kvm->arch.vgic.vctrl_base) + return -EEXIST;
/* * Any time a vcpu is run, vcpu_load is called which tries to grab the @@ -1659,9 +1655,6 @@ out_unlock: vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx); mutex_unlock(&vcpu->mutex); } - -out: - mutex_unlock(&kvm->lock); return ret; }
--- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -587,6 +587,11 @@ static void kvm_destroy_devices(struct k { struct list_head *node, *tmp;
+ /* + * We do not need to take the kvm->lock here, because nobody else + * has a reference to the struct kvm at this point and therefore + * cannot access the devices list anyhow. + */ list_for_each_safe(node, tmp, &kvm->devices) { struct kvm_device *dev = list_entry(node, struct kvm_device, vm_node); @@ -2322,11 +2327,15 @@ static int kvm_ioctl_create_device(struc dev->ops = ops; dev->kvm = kvm;
+ mutex_lock(&kvm->lock); ret = ops->create(dev, cd->type); if (ret < 0) { + mutex_unlock(&kvm->lock); kfree(dev); return ret; } + list_add(&dev->vm_node, &kvm->devices); + mutex_unlock(&kvm->lock);
if (ops->init) ops->init(dev); @@ -2334,10 +2343,12 @@ static int kvm_ioctl_create_device(struc ret = anon_inode_getfd(ops->name, &kvm_device_fops, dev, O_RDWR | O_CLOEXEC); if (ret < 0) { ops->destroy(dev); + mutex_lock(&kvm->lock); + list_del(&dev->vm_node); + mutex_unlock(&kvm->lock); return ret; }
- list_add(&dev->vm_node, &kvm->devices); kvm_get_kvm(kvm); cd->fd = ret; return 0;