From 149487bdacde32f5a9a344a49533ae0772fb9db7 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Mon, 21 Oct 2019 15:58:42 -0700 Subject: KVM: Add separate helper for putting borrowed reference to kvm Add a new helper, kvm_put_kvm_no_destroy(), to handle putting a borrowed reference[*] to the VM when installing a new file descriptor fails. KVM expects the refcount to remain valid in this case, as the in-progress ioctl() has an explicit reference to the VM. The primary motiviation for the helper is to document that the 'kvm' pointer is still valid after putting the borrowed reference, e.g. to document that doing mutex(&kvm->lock) immediately after putting a ref to kvm isn't broken. [*] When exposing a new object to userspace via a file descriptor, e.g. a new vcpu, KVM grabs a reference to itself (the VM) prior to making the object visible to userspace to avoid prematurely freeing the VM in the scenario where userspace immediately closes file descriptor. Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- virt/kvm/kvm_main.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) (limited to 'virt') diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 67ef3f2e19e8..b8534c6b8cf6 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -772,6 +772,18 @@ void kvm_put_kvm(struct kvm *kvm) } EXPORT_SYMBOL_GPL(kvm_put_kvm); +/* + * Used to put a reference that was taken on behalf of an object associated + * with a user-visible file descriptor, e.g. a vcpu or device, if installation + * of the new file descriptor fails and the reference cannot be transferred to + * its final owner. In such cases, the caller is still actively using @kvm and + * will fail miserably if the refcount unexpectedly hits zero. + */ +void kvm_put_kvm_no_destroy(struct kvm *kvm) +{ + WARN_ON(refcount_dec_and_test(&kvm->users_count)); +} +EXPORT_SYMBOL_GPL(kvm_put_kvm_no_destroy); static int kvm_vm_release(struct inode *inode, struct file *filp) { @@ -2679,7 +2691,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) kvm_get_kvm(kvm); r = create_vcpu_fd(vcpu); if (r < 0) { - kvm_put_kvm(kvm); + kvm_put_kvm_no_destroy(kvm); goto unlock_vcpu_destroy; } @@ -3117,7 +3129,7 @@ static int kvm_ioctl_create_device(struct kvm *kvm, kvm_get_kvm(kvm); ret = anon_inode_getfd(ops->name, &kvm_device_fops, dev, O_RDWR | O_CLOEXEC); if (ret < 0) { - kvm_put_kvm(kvm); + kvm_put_kvm_no_destroy(kvm); mutex_lock(&kvm->lock); list_del(&dev->vm_node); mutex_unlock(&kvm->lock); -- cgit v1.2.3 From b139b5a24774ee28e3e4d22942e2bede28d48202 Mon Sep 17 00:00:00 2001 From: Miaohe Lin Date: Sat, 9 Nov 2019 16:08:20 +0800 Subject: KVM: MMIO: get rid of odd out_err label in kvm_coalesced_mmio_init The out_err label and var ret is unnecessary, clean them up. Signed-off-by: Miaohe Lin Signed-off-by: Paolo Bonzini --- virt/kvm/coalesced_mmio.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) (limited to 'virt') diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c index 8ffd07e2a160..00c747dbc82e 100644 --- a/virt/kvm/coalesced_mmio.c +++ b/virt/kvm/coalesced_mmio.c @@ -110,14 +110,11 @@ static const struct kvm_io_device_ops coalesced_mmio_ops = { int kvm_coalesced_mmio_init(struct kvm *kvm) { struct page *page; - int ret; - ret = -ENOMEM; page = alloc_page(GFP_KERNEL | __GFP_ZERO); if (!page) - goto out_err; + return -ENOMEM; - ret = 0; kvm->coalesced_mmio_ring = page_address(page); /* @@ -128,8 +125,7 @@ int kvm_coalesced_mmio_init(struct kvm *kvm) spin_lock_init(&kvm->ring_lock); INIT_LIST_HEAD(&kvm->coalesced_zones); -out_err: - return ret; + return 0; } void kvm_coalesced_mmio_free(struct kvm *kvm) -- cgit v1.2.3 From 8750e72a79dda2f665ce17b62049f4d62130d991 Mon Sep 17 00:00:00 2001 From: Radim Krčmář Date: Thu, 7 Nov 2019 07:53:42 -0500 Subject: KVM: remember position in kvm->vcpus array MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Fetching an index for any vcpu in kvm->vcpus array by traversing the entire array everytime is costly. This patch remembers the position of each vcpu in kvm->vcpus array by storing it in vcpus_idx under kvm_vcpu structure. Signed-off-by: Radim Krčmář Signed-off-by: Nitesh Narayan Lal Signed-off-by: Paolo Bonzini --- include/linux/kvm_host.h | 11 +++-------- virt/kvm/kvm_main.c | 5 +++-- 2 files changed, 6 insertions(+), 10 deletions(-) (limited to 'virt') diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index a817e446c9aa..70b2296fb2ae 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -266,7 +266,8 @@ struct kvm_vcpu { struct preempt_notifier preempt_notifier; #endif int cpu; - int vcpu_id; + int vcpu_id; /* id given by userspace at creation */ + int vcpu_idx; /* index in kvm->vcpus array */ int srcu_idx; int mode; u64 requests; @@ -570,13 +571,7 @@ static inline struct kvm_vcpu *kvm_get_vcpu_by_id(struct kvm *kvm, int id) static inline int kvm_vcpu_get_idx(struct kvm_vcpu *vcpu) { - struct kvm_vcpu *tmp; - int idx; - - kvm_for_each_vcpu(idx, tmp, vcpu->kvm) - if (tmp == vcpu) - return idx; - BUG(); + return vcpu->vcpu_idx; } #define kvm_for_each_memslot(memslot, slots) \ diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index b8534c6b8cf6..a158a93323f7 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2685,7 +2685,8 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) goto unlock_vcpu_destroy; } - BUG_ON(kvm->vcpus[atomic_read(&kvm->online_vcpus)]); + vcpu->vcpu_idx = atomic_read(&kvm->online_vcpus); + BUG_ON(kvm->vcpus[vcpu->vcpu_idx]); /* Now it's all set up, let userspace reach it */ kvm_get_kvm(kvm); @@ -2695,7 +2696,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) goto unlock_vcpu_destroy; } - kvm->vcpus[atomic_read(&kvm->online_vcpus)] = vcpu; + kvm->vcpus[vcpu->vcpu_idx] = vcpu; /* * Pairs with smp_rmb() in kvm_get_vcpu. Write kvm->vcpus -- cgit v1.2.3 From faf0be22167486feb1ee386f0e819a336e829d0a Mon Sep 17 00:00:00 2001 From: Miaohe Lin Date: Sat, 23 Nov 2019 10:45:50 +0800 Subject: KVM: Fix jump label out_free_* in kvm_init() The jump label out_free_1 and out_free_2 deal with the same stuff, so git rid of one and rename the label out_free_0a to retain the label name order. Signed-off-by: Miaohe Lin Signed-off-by: Paolo Bonzini --- virt/kvm/kvm_main.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'virt') diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 13e6b7094596..00268290dcbd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4354,12 +4354,12 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, r = kvm_arch_hardware_setup(); if (r < 0) - goto out_free_0a; + goto out_free_1; for_each_online_cpu(cpu) { smp_call_function_single(cpu, check_processor_compat, &r, 1); if (r < 0) - goto out_free_1; + goto out_free_2; } r = cpuhp_setup_state_nocalls(CPUHP_AP_KVM_STARTING, "kvm/cpu:starting", @@ -4416,9 +4416,8 @@ out_free_3: unregister_reboot_notifier(&kvm_reboot_notifier); cpuhp_remove_state_nocalls(CPUHP_AP_KVM_STARTING); out_free_2: -out_free_1: kvm_arch_hardware_unsetup(); -out_free_0a: +out_free_1: free_cpumask_var(cpus_hardware_enabled); out_free_0: kvm_irqfd_exit(); -- cgit v1.2.3