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    SubjectRe: [RFC PATCH v3 8/8] vfio: Add nested IOPF support
    On Fri, 9 Apr 2021 11:44:20 +0800
    Shenming Lu <lushenming@huawei.com> wrote:

    > To set up nested mode, drivers such as vfio_pci need to register a
    > handler to receive stage/level 1 faults from the IOMMU, but since
    > currently each device can only have one iommu dev fault handler,
    > and if stage 2 IOPF is already enabled (VFIO_IOMMU_ENABLE_IOPF),
    > we choose to update the registered handler (a consolidated one) via
    > flags (set FAULT_REPORT_NESTED_L1), and further deliver the received
    > stage 1 faults in the handler to the guest through a newly added
    > vfio_device_ops callback.

    Are there proposed in-kernel drivers that would use any of these
    symbols?

    > Signed-off-by: Shenming Lu <lushenming@huawei.com>
    > ---
    > drivers/vfio/vfio.c | 81 +++++++++++++++++++++++++++++++++
    > drivers/vfio/vfio_iommu_type1.c | 49 +++++++++++++++++++-
    > include/linux/vfio.h | 12 +++++
    > 3 files changed, 141 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
    > index 44c8dfabf7de..4245f15914bf 100644
    > --- a/drivers/vfio/vfio.c
    > +++ b/drivers/vfio/vfio.c
    > @@ -2356,6 +2356,87 @@ struct iommu_domain *vfio_group_iommu_domain(struct vfio_group *group)
    > }
    > EXPORT_SYMBOL_GPL(vfio_group_iommu_domain);
    >
    > +/*
    > + * Register/Update the VFIO IOPF handler to receive
    > + * nested stage/level 1 faults.
    > + */
    > +int vfio_iommu_dev_fault_handler_register_nested(struct device *dev)
    > +{
    > + struct vfio_container *container;
    > + struct vfio_group *group;
    > + struct vfio_iommu_driver *driver;
    > + int ret;
    > +
    > + if (!dev)
    > + return -EINVAL;
    > +
    > + group = vfio_group_get_from_dev(dev);
    > + if (!group)
    > + return -ENODEV;
    > +
    > + ret = vfio_group_add_container_user(group);
    > + if (ret)
    > + goto out;
    > +
    > + container = group->container;
    > + driver = container->iommu_driver;
    > + if (likely(driver && driver->ops->register_handler))
    > + ret = driver->ops->register_handler(container->iommu_data, dev);
    > + else
    > + ret = -ENOTTY;
    > +
    > + vfio_group_try_dissolve_container(group);
    > +
    > +out:
    > + vfio_group_put(group);
    > + return ret;
    > +}
    > +EXPORT_SYMBOL_GPL(vfio_iommu_dev_fault_handler_register_nested);
    > +
    > +int vfio_iommu_dev_fault_handler_unregister_nested(struct device *dev)
    > +{
    > + struct vfio_container *container;
    > + struct vfio_group *group;
    > + struct vfio_iommu_driver *driver;
    > + int ret;
    > +
    > + if (!dev)
    > + return -EINVAL;
    > +
    > + group = vfio_group_get_from_dev(dev);
    > + if (!group)
    > + return -ENODEV;
    > +
    > + ret = vfio_group_add_container_user(group);
    > + if (ret)
    > + goto out;
    > +
    > + container = group->container;
    > + driver = container->iommu_driver;
    > + if (likely(driver && driver->ops->unregister_handler))
    > + ret = driver->ops->unregister_handler(container->iommu_data, dev);
    > + else
    > + ret = -ENOTTY;
    > +
    > + vfio_group_try_dissolve_container(group);
    > +
    > +out:
    > + vfio_group_put(group);
    > + return ret;
    > +}
    > +EXPORT_SYMBOL_GPL(vfio_iommu_dev_fault_handler_unregister_nested);
    > +
    > +int vfio_transfer_iommu_fault(struct device *dev, struct iommu_fault *fault)
    > +{
    > + struct vfio_device *device = dev_get_drvdata(dev);
    > +
    > + if (unlikely(!device->ops->transfer))
    > + return -EOPNOTSUPP;
    > +
    > + return device->ops->transfer(device->device_data, fault);
    > +}
    > +EXPORT_SYMBOL_GPL(vfio_transfer_iommu_fault);
    > +
    > /**
    > * Module/class support
    > */
    > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
    > index ba2b5a1cf6e9..9d1adeddb303 100644
    > --- a/drivers/vfio/vfio_iommu_type1.c
    > +++ b/drivers/vfio/vfio_iommu_type1.c
    > @@ -3821,13 +3821,32 @@ static int vfio_iommu_type1_dma_map_iopf(struct iommu_fault *fault, void *data)
    > struct vfio_batch batch;
    > struct vfio_range *range;
    > dma_addr_t iova = ALIGN_DOWN(fault->prm.addr, PAGE_SIZE);
    > - int access_flags = 0;
    > + int access_flags = 0, nested;
    > size_t premap_len, map_len, mapped_len = 0;
    > unsigned long bit_offset, vaddr, pfn, i, npages;
    > int ret;
    > enum iommu_page_response_code status = IOMMU_PAGE_RESP_INVALID;
    > struct iommu_page_response resp = {0};
    >
    > + if (vfio_dev_domian_nested(dev, &nested))
    > + return -ENODEV;
    > +
    > + /*
    > + * When configured in nested mode, further deliver the
    > + * stage/level 1 faults to the guest.
    > + */
    > + if (nested) {
    > + bool l2;
    > +
    > + if (fault->type == IOMMU_FAULT_PAGE_REQ)
    > + l2 = fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_L2;
    > + if (fault->type == IOMMU_FAULT_DMA_UNRECOV)
    > + l2 = fault->event.flags & IOMMU_FAULT_UNRECOV_L2;
    > +
    > + if (!l2)
    > + return vfio_transfer_iommu_fault(dev, fault);
    > + }
    > +
    > if (fault->type != IOMMU_FAULT_PAGE_REQ)
    > return -EOPNOTSUPP;
    >
    > @@ -4201,6 +4220,32 @@ static void vfio_iommu_type1_notify(void *iommu_data,
    > wake_up_all(&iommu->vaddr_wait);
    > }
    >
    > +static int vfio_iommu_type1_register_handler(void *iommu_data,
    > + struct device *dev)
    > +{
    > + struct vfio_iommu *iommu = iommu_data;
    > +
    > + if (iommu->iopf_enabled)
    > + return iommu_update_device_fault_handler(dev, ~0,
    > + FAULT_REPORT_NESTED_L1);
    > + else
    > + return iommu_register_device_fault_handler(dev,
    > + vfio_iommu_type1_dma_map_iopf,
    > + FAULT_REPORT_NESTED_L1, dev);
    > +}
    > +
    > +static int vfio_iommu_type1_unregister_handler(void *iommu_data,
    > + struct device *dev)
    > +{
    > + struct vfio_iommu *iommu = iommu_data;
    > +
    > + if (iommu->iopf_enabled)
    > + return iommu_update_device_fault_handler(dev,
    > + ~FAULT_REPORT_NESTED_L1, 0);
    > + else
    > + return iommu_unregister_device_fault_handler(dev);
    > +}


    The path through vfio to register this is pretty ugly, but I don't see
    any reason for the the update interfaces here, the previously
    registered handler just changes its behavior.


    > +
    > static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
    > .name = "vfio-iommu-type1",
    > .owner = THIS_MODULE,
    > @@ -4216,6 +4261,8 @@ static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
    > .dma_rw = vfio_iommu_type1_dma_rw,
    > .group_iommu_domain = vfio_iommu_type1_group_iommu_domain,
    > .notify = vfio_iommu_type1_notify,
    > + .register_handler = vfio_iommu_type1_register_handler,
    > + .unregister_handler = vfio_iommu_type1_unregister_handler,
    > };
    >
    > static int __init vfio_iommu_type1_init(void)
    > diff --git a/include/linux/vfio.h b/include/linux/vfio.h
    > index a7b426d579df..4621d8f0395d 100644
    > --- a/include/linux/vfio.h
    > +++ b/include/linux/vfio.h
    > @@ -29,6 +29,8 @@
    > * @match: Optional device name match callback (return: 0 for no-match, >0 for
    > * match, -errno for abort (ex. match with insufficient or incorrect
    > * additional args)
    > + * @transfer: Optional. Transfer the received stage/level 1 faults to the guest
    > + * for nested mode.
    > */
    > struct vfio_device_ops {
    > char *name;
    > @@ -43,6 +45,7 @@ struct vfio_device_ops {
    > int (*mmap)(void *device_data, struct vm_area_struct *vma);
    > void (*request)(void *device_data, unsigned int count);
    > int (*match)(void *device_data, char *buf);
    > + int (*transfer)(void *device_data, struct iommu_fault *fault);
    > };
    >
    > extern struct iommu_group *vfio_iommu_group_get(struct device *dev);
    > @@ -100,6 +103,10 @@ struct vfio_iommu_driver_ops {
    > struct iommu_group *group);
    > void (*notify)(void *iommu_data,
    > enum vfio_iommu_notify_type event);
    > + int (*register_handler)(void *iommu_data,
    > + struct device *dev);
    > + int (*unregister_handler)(void *iommu_data,
    > + struct device *dev);
    > };
    >
    > extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
    > @@ -161,6 +168,11 @@ extern int vfio_unregister_notifier(struct device *dev,
    > struct kvm;
    > extern void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm);
    >
    > +extern int vfio_iommu_dev_fault_handler_register_nested(struct device *dev);
    > +extern int vfio_iommu_dev_fault_handler_unregister_nested(struct device *dev);
    > +extern int vfio_transfer_iommu_fault(struct device *dev,
    > + struct iommu_fault *fault);
    > +
    > /*
    > * Sub-module helpers
    > */

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