Re: [PATCH v5] vfio/pci: Propagate ACPI notifications to user-space via eventfd

To allow pass-through devices receiving ACPI notifications, permit to register ACPI notify handler (via VFIO_DEVICE_SET_IRQS) for a given device. The handler role is to receive and propagate such ACPI notifications to the user-space through the user provided eventfd. This allows VMM to receive and propagate them further to the VM, where the actual driver for pass-through device resides and can react to device specific notifications accordingly. The eventfd usage ensures VMM and device isolation: it allows to use a dedicated channel associated with the device for such events, such that the VMM has direct access. Since the eventfd counter is used as ACPI notification value placeholder, the eventfd signaling needs to be serialized in order to not end up with notification values being coalesced. Therefore ACPI notification values are buffered and signalized one by one, when the previous notification value has been consumed. Signed-off-by: Grzegorz Jaszczyk <jaz(a)semihalf.com&gt; --- Changelog v4..v5 Address Alex Williamson's feedback: - s/vfio_acpi_notify.{c,o}/acpi_notify.{c,o} - Do not put acpi_notify to its own module but fold it into main vfio.ko. Additionally select it from VFIO_PCI_CORE instead of VFIO_PCI. - Cleanup acpi notify under igate mutex (in vfio_pci_core_close_device). - Add extra check for ACPI companion in vfio_pci_get_irq_count and extend vfio_pci_ioctl_get_irq_info. - Drop acpi.h include - linux/vfio_acpi_notify.h includes it already. - Send device check notification value for DATA_NONE and non-zero count and for DATA_BOOL and non-zero count (as for loopback testing). - Drop some redundant !acpi_notify->acpi_notify_trigger checks. - Move some common code to new helper functions: 1) acpi_notification_dequeue 2) vfio_acpi_notify_cleanup and rename previous vfio_acpi_notify_cleanup into vfio_remove_acpi_notify which uses it - Add rate limited logging for dropped notifications. - Move vdev->acpi_notification pointer cleanup to the vfio_acpi_notify_cleanup function this also fixes two bigger issues caught by Alex. - Allow the eventfd to be swapped. - s/GFP_KERNEL/GFP_KERNEL_ACCOUNT. - s/VFIO_PCI_ACPI_NTFY_IRQ_INDEX/VFIO_PCI_ACPI_IRQ_INDEX. - Add header protection for multiple includes. - v4: https://patchwork.kernel.org/project/kvm/patch/20230522165811.123417-1-ja... Changelog v3..v4 Address Alex Williamson feedback: - Instead of introducing new ioctl used for eventfd registration, take advantage of VFIO_DEVICE_SET_IRQS which already supports virtual IRQs for things like error notification and device release requests. - Introduced mechanism preventing creation of large queues. Other: - Move the implementation into the newly introduced VFIO_ACPI_NOTIFY helper module. It is actually not bound to VFIO_PCI but VFIO_PCI enables it whenever ACPI support is enabled. This change is introduced since ACPI notifications are not limited to PCI devices, making it PCI independent will allow to re-use it also for other VFIO_* like supports: e.g. VFIO_PLATFORM in the future if needed. Moving it out of drivers/vfio/pci/ was also suggested offline. - s/notify_val_next/node - v3: https://patchwork.kernel.org/project/kvm/patch/20230502132700.654528-1-ja... Changelog v2..v3: - Fix compilation warnings when building with "W=1" Changelog v1..v2: - The v2 implementation is actually completely different then v1: instead of using acpi netlink events for propagating ACPI notifications to the user space take advantage of eventfd, which can provide better VMM and device isolation: it allows to use a dedicated channel associated with the device for such events, such that the VMM has direct access. - Using eventfd counter as notification value placeholder was suggested in v1 and requires additional serialization logic introduced in v2. - Since the vfio-pci supports non-ACPI platforms address !CONFIG_ACPI case. - v1 discussion: https://patchwork.kernel.org/project/kvm/patch/20230307220553.631069-1-ja... --- drivers/vfio/Kconfig | 5 + drivers/vfio/Makefile | 1 + drivers/vfio/acpi_notify.c | 249 ++++++++++++++++++++++++++++++ drivers/vfio/pci/Kconfig | 1 + drivers/vfio/pci/vfio_pci_core.c | 13 ++ drivers/vfio/pci/vfio_pci_intrs.c | 85 ++++++++++ include/linux/vfio_acpi_notify.h | 45 ++++++ include/linux/vfio_pci_core.h | 1 + include/uapi/linux/vfio.h | 1 + 9 files changed, 401 insertions(+) create mode 100644 drivers/vfio/acpi_notify.c create mode 100644 include/linux/vfio_acpi_notify.h diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig index 89e06c981e43..cd9df43a4eb4 100644 --- a/drivers/vfio/Kconfig +++ b/drivers/vfio/Kconfig @@ -12,6 +12,11 @@ menuconfig VFIO If you don't know what to do here, say N. if VFIO +config VFIO_ACPI_NOTIFY + bool + depends on ACPI + default n + config VFIO_CONTAINER bool "Support for the VFIO container /dev/vfio/vfio" select VFIO_IOMMU_TYPE1 if MMU && (X86 || S390 || ARM || ARM64) diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile index 70e7dcb302ef..003c2b041785 100644 --- a/drivers/vfio/Makefile +++ b/drivers/vfio/Makefile @@ -7,6 +7,7 @@ vfio-y += vfio_main.o \ vfio-$(CONFIG_IOMMUFD) += iommufd.o vfio-$(CONFIG_VFIO_CONTAINER) += container.o vfio-$(CONFIG_VFIO_VIRQFD) += virqfd.o +vfio-$(CONFIG_VFIO_ACPI_NOTIFY) += acpi_notify.o obj-$(CONFIG_VFIO_IOMMU_TYPE1) += vfio_iommu_type1.o obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o diff --git a/drivers/vfio/acpi_notify.c b/drivers/vfio/acpi_notify.c new file mode 100644 index 000000000000..8d3f063502fe --- /dev/null +++ b/drivers/vfio/acpi_notify.c @@ -0,0 +1,249 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * VFIO ACPI notification propagation + * + * Author: Grzegorz Jaszczyk <jaz(a)semihalf.com&gt; + */ +#include <linux/vfio_acpi_notify.h> + +#define NOTIFICATION_QUEUE_SIZE 20 + +struct notification_queue { + int notification_val; + struct list_head node; +}; + +static int vfio_eventfd_wakeup(wait_queue_entry_t *wait, unsigned int mode, + int sync, void *key) +{ + struct vfio_acpi_notification *acpi_notify = + container_of(wait, struct vfio_acpi_notification, wait); + __poll_t flags = key_to_poll(key);

+ + /* + * eventfd_read signalize EPOLLOUT at the end of its function - this + * means previous eventfd with its notification value was consumed so + * the next notification can be signalized now if pending - schedule + * proper work. + */ + if (flags & EPOLLOUT) { + mutex_unlock(&acpi_notify->notification_lock); + schedule_work(&acpi_notify->acpi_notification_work); + }

+ + return 0; +} + +static void vfio_ptable_queue_proc(struct file *file, + wait_queue_head_t *wqh, poll_table *pt) +{ + struct vfio_acpi_notification *acpi_notify = + container_of(pt, struct vfio_acpi_notification, pt); + + add_wait_queue(wqh, &acpi_notify->wait); +} + +static struct notification_queue * +acpi_notification_dequeue(struct vfio_acpi_notification *acpi_notify) +{ + struct notification_queue *oldest_entry; +

+ oldest_entry = list_first_entry(&acpi_notify->notification_list, + struct notification_queue, + node); + list_del(&oldest_entry->node); + acpi_notify->notification_queue_count--; + + return oldest_entry; +} + +static void acpi_notification_work_fn(struct work_struct *work) +{ + struct vfio_acpi_notification *acpi_notify; + struct notification_queue *entry; + + acpi_notify = container_of(work, struct vfio_acpi_notification, + acpi_notification_work); + + mutex_lock(&acpi_notify->notification_list_lock); + if (list_empty(&acpi_notify->notification_list)) + goto out; + + /* + * If the previous eventfd was not yet consumed by user-space lets hold + * on and exit. The notification function will be rescheduled when + * signaling eventfd will be possible (when the EPOLLOUT will be + * signalized and unlocks notify_events). + */ + if (!mutex_trylock(&acpi_notify->notification_lock)) + goto out; + + entry = acpi_notification_dequeue(acpi_notify); + + mutex_unlock(&acpi_notify->notification_list_lock); + + eventfd_signal(acpi_notify->acpi_notify_trigger, entry->notification_val); + + kfree(entry); + + return; +out: + mutex_unlock(&acpi_notify->notification_list_lock); +} + +static void +vfio_acpi_notify_cleanup(struct vfio_acpi_notification **acpi_notify_ptr, + struct acpi_device *adev) +{ + struct vfio_acpi_notification *acpi_notify = *acpi_notify_ptr; + struct notification_queue *entry, *entry_tmp; + u64 cnt; + + eventfd_ctx_remove_wait_queue(acpi_notify->acpi_notify_trigger, + &acpi_notify->wait, &cnt); + + flush_work(&acpi_notify->acpi_notification_work);

+ + mutex_lock(&acpi_notify->notification_list_lock); + list_for_each_entry_safe(entry, entry_tmp, + &acpi_notify->notification_list, + node) { + list_del(&entry->node); + kfree(entry); + } + mutex_unlock(&acpi_notify->notification_list_lock); + + eventfd_ctx_put(acpi_notify->acpi_notify_trigger); + + kfree(acpi_notify); + + *acpi_notify_ptr = NULL; +} + +void vfio_acpi_notify(acpi_handle handle, u32 event, void *data) +{ + struct vfio_acpi_notification *acpi_notify = (struct vfio_acpi_notification *)data; + struct notification_queue *entry; + + entry = kmalloc(sizeof(*entry), GFP_KERNEL); + if (!entry) + return; + + entry->notification_val = event; + INIT_LIST_HEAD(&entry->node); + + mutex_lock(&acpi_notify->notification_list_lock); + if (acpi_notify->notification_queue_count > NOTIFICATION_QUEUE_SIZE) { + struct notification_queue *oldest_entry = + acpi_notification_dequeue(acpi_notify); + + if (printk_ratelimit()) + acpi_handle_warn(handle, + "dropping notification value %d\n", + oldest_entry->notification_val); + + kfree(oldest_entry); + } + list_add_tail(&entry->node, &acpi_notify->notification_list); + acpi_notify->notification_queue_count++; + mutex_unlock(&acpi_notify->notification_list_lock); + + schedule_work(&acpi_notify->acpi_notification_work); +} +EXPORT_SYMBOL_GPL(vfio_acpi_notify); + +void vfio_remove_acpi_notify(struct vfio_acpi_notification **acpi_notify_ptr, + struct acpi_device *adev) +{ + struct vfio_acpi_notification *acpi_notify = *acpi_notify_ptr; + + if (!acpi_notify) + return; + + acpi_remove_notify_handler(adev->handle, ACPI_DEVICE_NOTIFY, + vfio_acpi_notify); + + vfio_acpi_notify_cleanup(acpi_notify_ptr, adev); +} +EXPORT_SYMBOL_GPL(vfio_remove_acpi_notify); + +int vfio_register_acpi_notify_handler(struct vfio_acpi_notification **acpi_notify_ptr, + struct acpi_device *adev, int32_t fd) +{ + struct vfio_acpi_notification *acpi_notify = *acpi_notify_ptr; + struct file *acpi_notify_trigger_file; + struct eventfd_ctx *efdctx; + acpi_status status; + + if (fd < -1) + return -EINVAL; + else if (fd == -1) { + vfio_remove_acpi_notify(acpi_notify_ptr, adev); + return 0; + } + + efdctx = eventfd_ctx_fdget(fd); + if (IS_ERR(efdctx)) + return PTR_ERR(efdctx); + + /* Allow eventfd to be swapped */ + if (acpi_notify) { + u64 cnt; + + acpi_notify_trigger_file = eventfd_fget(fd);

+ + mutex_lock(&acpi_notify->notification_lock);

+ eventfd_ctx_remove_wait_queue(acpi_notify->acpi_notify_trigger, + &acpi_notify->wait, &cnt); + eventfd_ctx_put(acpi_notify->acpi_notify_trigger); + acpi_notify->acpi_notify_trigger = efdctx; + vfs_poll(acpi_notify_trigger_file, &acpi_notify->pt); + mutex_unlock(&acpi_notify->notification_lock); + + /* + * The ACPI notifications could arrive and be queued during + * eventfd swap, retrigger the worker after notification + * replication unlocking. + */ + schedule_work(&acpi_notify->acpi_notification_work); + + return 0; + } + + acpi_notify = kzalloc(sizeof(*acpi_notify), GFP_KERNEL_ACCOUNT); + if (!acpi_notify) + return -ENOMEM; + + *acpi_notify_ptr = acpi_notify; + + INIT_WORK(&acpi_notify->acpi_notification_work, acpi_notification_work_fn); + INIT_LIST_HEAD(&acpi_notify->notification_list); + + acpi_notify->acpi_notify_trigger = efdctx; + + mutex_init(&acpi_notify->notification_lock); + + /* + * Install custom wake-up handler to be notified whenever underlying + * eventfd is consumed by the user-space. + */ + init_waitqueue_func_entry(&acpi_notify->wait, vfio_eventfd_wakeup); + init_poll_funcptr(&acpi_notify->pt, vfio_ptable_queue_proc); + + acpi_notify_trigger_file = eventfd_fget(fd); + vfs_poll(acpi_notify_trigger_file, &acpi_notify->pt); + + status = acpi_install_notify_handler(adev->handle, ACPI_DEVICE_NOTIFY, + vfio_acpi_notify, (void *)acpi_notify); + if (ACPI_FAILURE(status)) { + dev_err(&adev->dev, "Failed to install notify handler: %s", + acpi_format_exception(status)); + + vfio_acpi_notify_cleanup(acpi_notify_ptr, adev); + + return -ENODEV; + } + + return 0; +} +EXPORT_SYMBOL_GPL(vfio_register_acpi_notify_handler); diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig index f9d0c908e738..f03ca773dfd9 100644 --- a/drivers/vfio/pci/Kconfig +++ b/drivers/vfio/pci/Kconfig @@ -4,6 +4,7 @@ config VFIO_PCI_CORE tristate select VFIO_VIRQFD select IRQ_BYPASS_MANAGER + select VFIO_ACPI_NOTIFY if ACPI config VFIO_PCI_MMAP def_bool y if !S390 diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index a5ab416cf476..1cc4a9c05403 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -27,6 +27,7 @@ #include <linux/vgaarb.h> #include <linux/nospec.h> #include <linux/sched/mm.h> +#include <linux/vfio_acpi_notify.h> #if IS_ENABLED(CONFIG_EEH) #include <asm/eeh.h> #endif @@ -683,6 +684,7 @@ void vfio_pci_core_close_device(struct vfio_device *core_vdev) { struct vfio_pci_core_device *vdev = container_of(core_vdev, struct vfio_pci_core_device, vdev); + struct acpi_device *adev = ACPI_COMPANION(&vdev->pdev->dev); if (vdev->sriov_pf_core_dev) { mutex_lock(&vdev->sriov_pf_core_dev->vf_token->lock); @@ -704,6 +706,8 @@ void vfio_pci_core_close_device(struct vfio_device *core_vdev) eventfd_ctx_put(vdev->req_trigger); vdev->req_trigger = NULL; } + if (adev) + vfio_remove_acpi_notify(&vdev->acpi_notification, adev); mutex_unlock(&vdev->igate); } EXPORT_SYMBOL_GPL(vfio_pci_core_close_device); @@ -725,6 +729,8 @@ EXPORT_SYMBOL_GPL(vfio_pci_core_finish_enable); static int vfio_pci_get_irq_count(struct vfio_pci_core_device *vdev, int irq_type) { + struct acpi_device *adev = ACPI_COMPANION(&vdev->pdev->dev); + if (irq_type == VFIO_PCI_INTX_IRQ_INDEX) { u8 pin; @@ -761,6 +767,8 @@ static int vfio_pci_get_irq_count(struct vfio_pci_core_device *vdev, int irq_typ return 1; } else if (irq_type == VFIO_PCI_REQ_IRQ_INDEX) { return 1; + } else if (adev && irq_type == VFIO_PCI_ACPI_IRQ_INDEX) { + return 1; } return 0; @@ -1084,6 +1092,7 @@ static int vfio_pci_ioctl_get_irq_info(struct vfio_pci_core_device *vdev, struct vfio_irq_info __user *arg) { unsigned long minsz = offsetofend(struct vfio_irq_info, count); + struct acpi_device *adev = ACPI_COMPANION(&vdev->pdev->dev); struct vfio_irq_info info; if (copy_from_user(&info, arg, minsz)) @@ -1096,6 +1105,10 @@ static int vfio_pci_ioctl_get_irq_info(struct vfio_pci_core_device *vdev, case VFIO_PCI_INTX_IRQ_INDEX ... VFIO_PCI_MSIX_IRQ_INDEX: case VFIO_PCI_REQ_IRQ_INDEX: break; + case VFIO_PCI_ACPI_IRQ_INDEX: + if (adev) + break; + return -EINVAL; case VFIO_PCI_ERR_IRQ_INDEX: if (pci_is_pcie(vdev->pdev)) break; diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c index bffb0741518b..410f517f8b2c 100644 --- a/drivers/vfio/pci/vfio_pci_intrs.c +++ b/drivers/vfio/pci/vfio_pci_intrs.c @@ -19,6 +19,7 @@ #include <linux/vfio.h> #include <linux/wait.h> #include <linux/slab.h> +#include <linux/vfio_acpi_notify.h> #include "vfio_pci_priv.h" @@ -667,6 +668,76 @@ static int vfio_pci_set_req_trigger(struct vfio_pci_core_device *vdev, count, flags, data); } +static int +vfio_pci_set_acpi_ntfy_trigger(struct vfio_pci_core_device *vdev, + unsigned int index, unsigned int start, + unsigned int count, uint32_t flags, void *data) +{ + struct acpi_device *adev = ACPI_COMPANION(&vdev->pdev->dev); + acpi_handle handle; + + if (index != VFIO_PCI_ACPI_IRQ_INDEX || start != 0 || count > 1) + return -EINVAL; + + if (!adev) + return -ENODEV; + + if (!vdev->acpi_notification) + return -EINVAL; + +#if IS_ENABLED(CONFIG_ACPI) + handle = adev->handle; +#endif

+ + /* + * Disable notifications: flags = (DATA_NONE|ACTION_TRIGGER), count = 0 + * Enable loopback testing: (DATA_BOOL|ACTION_TRIGGER) or + * (DATA_NONE|ACTION_TRIGGER), count != 0 + */ + if (flags & VFIO_IRQ_SET_DATA_NONE) { + if (count) + vfio_acpi_notify(handle, ACPI_NOTIFY_DEVICE_CHECK, + vdev->acpi_notification); + else + vfio_remove_acpi_notify(&vdev->acpi_notification, adev); + + return 0; + } else if (flags & VFIO_IRQ_SET_DATA_BOOL) { + uint8_t trigger; + + if (!count) + return -EINVAL; + + trigger = *(uint8_t *)data; + if (trigger) + vfio_acpi_notify(handle, ACPI_NOTIFY_DEVICE_CHECK, + vdev->acpi_notification); + + return 0; + } + + return -EINVAL; +} + +static int +vfio_pci_set_acpi_ntfy_eventfd_trigger(struct vfio_pci_core_device *vdev, + unsigned int index, unsigned int start, + unsigned int count, uint32_t flags, void *data) +{ + struct acpi_device *adev = ACPI_COMPANION(&vdev->pdev->dev); + int32_t fd; + + if (index != VFIO_PCI_ACPI_IRQ_INDEX || start != 0 || count != 1) + return -EINVAL; + + if (!adev) + return -ENODEV; + + fd = *(int32_t *)data; + + return vfio_register_acpi_notify_handler(&vdev->acpi_notification, adev, fd); +} + int vfio_pci_set_irqs_ioctl(struct vfio_pci_core_device *vdev, uint32_t flags, unsigned index, unsigned start, unsigned count, void *data) @@ -716,6 +787,20 @@ int vfio_pci_set_irqs_ioctl(struct vfio_pci_core_device *vdev, uint32_t flags, break; } break; + case VFIO_PCI_ACPI_IRQ_INDEX: + switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) { + case VFIO_IRQ_SET_ACTION_TRIGGER: + switch (flags & VFIO_IRQ_SET_DATA_TYPE_MASK) { + case VFIO_IRQ_SET_DATA_BOOL: + case VFIO_IRQ_SET_DATA_NONE: + func = vfio_pci_set_acpi_ntfy_trigger; + break; + case VFIO_IRQ_SET_DATA_EVENTFD: + func = vfio_pci_set_acpi_ntfy_eventfd_trigger; + break; + } + } + break; } if (!func) diff --git a/include/linux/vfio_acpi_notify.h b/include/linux/vfio_acpi_notify.h new file mode 100644 index 000000000000..4bf1d055a014 --- /dev/null +++ b/include/linux/vfio_acpi_notify.h @@ -0,0 +1,45 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * VFIO ACPI notification replication + * + * Author: Grzegorz Jaszczyk <jaz(a)semihalf.com&gt; + */ +#include <linux/acpi.h> +#include <linux/eventfd.h> +#include <linux/poll.h> + +#ifndef VFIO_ACPI_NOTIFY_H +#define VFIO_ACPI_NOTIFY_H + +struct vfio_acpi_notification { + struct eventfd_ctx *acpi_notify_trigger; + struct work_struct acpi_notification_work; + struct list_head notification_list; + struct mutex notification_list_lock; + struct mutex notification_lock; + int notification_queue_count; + poll_table pt; + wait_queue_entry_t wait; +}; + +#if IS_ENABLED(CONFIG_ACPI) +void vfio_acpi_notify(acpi_handle handle, u32 event, void *data); +int vfio_register_acpi_notify_handler(struct vfio_acpi_notification **acpi_notify, + struct acpi_device *adev, int32_t fd); +void vfio_remove_acpi_notify(struct vfio_acpi_notification **acpi_notify, + struct acpi_device *adev); +#else +static inline void vfio_acpi_notify(acpi_handle handle, u32 event, void *data) {} +static inline int +vfio_register_acpi_notify_handler(struct vfio_acpi_notification **acpi_notify, + struct acpi_device *adev, int32_t fd) +{ + return -ENODEV; +} + +static inline void +vfio_remove_acpi_notify(struct vfio_acpi_notification **acpi_notify, + struct acpi_device *adev) {} +#endif /* CONFIG_ACPI */ + +#endif /* VFIO_ACPI_NOTIFY_H */ diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h index 367fd79226a3..a4491b3d8064 100644 --- a/include/linux/vfio_pci_core.h +++ b/include/linux/vfio_pci_core.h @@ -96,6 +96,7 @@ struct vfio_pci_core_device { struct mutex vma_lock; struct list_head vma_list; struct rw_semaphore memory_lock; + struct vfio_acpi_notification *acpi_notification; }; /* Will be exported for vfio pci drivers usage */ diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h index 0552e8dcf0cb..6b20ef3d202c 100644 --- a/include/uapi/linux/vfio.h +++ b/include/uapi/linux/vfio.h @@ -625,6 +625,7 @@ enum { VFIO_PCI_MSIX_IRQ_INDEX, VFIO_PCI_ERR_IRQ_INDEX, VFIO_PCI_REQ_IRQ_INDEX, + VFIO_PCI_ACPI_IRQ_INDEX, VFIO_PCI_NUM_IRQS };