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SubjectRe: [PATCH v10 2/4] uacce: add uacce driver
On Mon, 16 Dec 2019 11:08:15 +0800
Zhangfei Gao <zhangfei.gao@linaro.org> wrote:

> From: Kenneth Lee <liguozhu@hisilicon.com>
>
> Uacce (Unified/User-space-access-intended Accelerator Framework) targets to
> provide Shared Virtual Addressing (SVA) between accelerators and processes.
> So accelerator can access any data structure of the main cpu.
> This differs from the data sharing between cpu and io device, which share
> only data content rather than address.
> Since unified address, hardware and user space of process can share the
> same virtual address in the communication.
>
> Uacce create a chrdev for every registration, the queue is allocated to
> the process when the chrdev is opened. Then the process can access the
> hardware resource by interact with the queue file. By mmap the queue
> file space to user space, the process can directly put requests to the
> hardware without syscall to the kernel space.
>
> The IOMMU core only tracks mm<->device bonds at the moment, because it
> only needs to handle IOTLB invalidation and PASID table entries. However
> uacce needs a finer granularity since multiple queues from the same
> device can be bound to an mm. When the mm exits, all bound queues must
> be stopped so that the IOMMU can safely clear the PASID table entry and
> reallocate the PASID.
>
> An intermediate struct uacce_mm links uacce devices and queues.
> Note that an mm may be bound to multiple devices but an uacce_mm
> structure only ever belongs to a single device, because we don't need
> anything more complex (if multiple devices are bound to one mm, then
> we'll create one uacce_mm for each bond).
>
> uacce_device --+-- uacce_mm --+-- uacce_queue
> | '-- uacce_queue
> |
> '-- uacce_mm --+-- uacce_queue
> +-- uacce_queue
> '-- uacce_queue
>
> Signed-off-by: Kenneth Lee <liguozhu@hisilicon.com>
> Signed-off-by: Zaibo Xu <xuzaibo@huawei.com>
> Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>

Hi,

Two small things I'd missed previously. Fix those and for
what it's worth

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
> Documentation/ABI/testing/sysfs-driver-uacce | 37 ++
> drivers/misc/Kconfig | 1 +
> drivers/misc/Makefile | 1 +
> drivers/misc/uacce/Kconfig | 13 +
> drivers/misc/uacce/Makefile | 2 +
> drivers/misc/uacce/uacce.c | 628 +++++++++++++++++++++++++++
> include/linux/uacce.h | 161 +++++++
> include/uapi/misc/uacce/uacce.h | 38 ++
> 8 files changed, 881 insertions(+)
> create mode 100644 Documentation/ABI/testing/sysfs-driver-uacce
> create mode 100644 drivers/misc/uacce/Kconfig
> create mode 100644 drivers/misc/uacce/Makefile
> create mode 100644 drivers/misc/uacce/uacce.c
> create mode 100644 include/linux/uacce.h
> create mode 100644 include/uapi/misc/uacce/uacce.h
>
...
> +
> +What: /sys/class/uacce/<dev_name>/available_instances
> +Date: Dec 2019
> +KernelVersion: 5.6
> +Contact: linux-accelerators@lists.ozlabs.org
> +Description: Available instances left of the device
> + Return -ENODEV if uacce_ops get_available_instances is not provided
> +

See below. It doesn't "return" it prints it currently.

...

> +static int uacce_fops_mmap(struct file *filep, struct vm_area_struct *vma)
> +{
> + struct uacce_queue *q = filep->private_data;
> + struct uacce_device *uacce = q->uacce;
> + struct uacce_qfile_region *qfr;
> + enum uacce_qfrt type = UACCE_MAX_REGION;
> + int ret = 0;
> +
> + if (vma->vm_pgoff < UACCE_MAX_REGION)
> + type = vma->vm_pgoff;
> + else
> + return -EINVAL;
> +
> + qfr = kzalloc(sizeof(*qfr), GFP_KERNEL);
> + if (!qfr)
> + return -ENOMEM;
> +
> + vma->vm_flags |= VM_DONTCOPY | VM_DONTEXPAND | VM_WIPEONFORK;
> + vma->vm_ops = &uacce_vm_ops;
> + vma->vm_private_data = q;
> + qfr->type = type;
> +
> + mutex_lock(&uacce_mutex);
> +
> + if (q->state != UACCE_Q_INIT && q->state != UACCE_Q_STARTED) {
> + ret = -EINVAL;
> + goto out_with_lock;
> + }
> +
> + if (q->qfrs[type]) {
> + ret = -EEXIST;
> + goto out_with_lock;
> + }
> +
> + switch (type) {
> + case UACCE_QFRT_MMIO:
> + if (!uacce->ops->mmap) {
> + ret = -EINVAL;
> + goto out_with_lock;
> + }
> +
> + ret = uacce->ops->mmap(q, vma, qfr);
> + if (ret)
> + goto out_with_lock;
> +
> + break;
> +
> + case UACCE_QFRT_DUS:
> + if (uacce->flags & UACCE_DEV_SVA) {
> + if (!uacce->ops->mmap) {
> + ret = -EINVAL;
> + goto out_with_lock;
> + }
> +
> + ret = uacce->ops->mmap(q, vma, qfr);
> + if (ret)
> + goto out_with_lock;
> + }

Slightly odd corner case, but what stops us getting here with
the UACCE_DEV_SVA flag not set? If that happened I'd expect to
return an error but looks like we return 0.



> + break;
> +
> + default:
> + ret = -EINVAL;
> + goto out_with_lock;
> + }
> +
> + q->qfrs[type] = qfr;
> + mutex_unlock(&uacce_mutex);
> +
> + return ret;
> +
> +out_with_lock:
> + mutex_unlock(&uacce_mutex);
> + kfree(qfr);
> + return ret;
> +}

...

> +static ssize_t available_instances_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct uacce_device *uacce = to_uacce_device(dev);
> + int val = -ENODEV;
> +
> + if (uacce->ops->get_available_instances)
> + val = uacce->ops->get_available_instances(uacce);
> +
> + return sprintf(buf, "%d\n", val);

It's unusual to pass an error value back as a string.
I'd expect some logic like..

if (val < 0)
return val;

return sprintf(buf, "%d\n", val);

Note this is the documented behavior "returns -ENODEV".

> +}
> +
> +static ssize_t algorithms_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct uacce_device *uacce = to_uacce_device(dev);
> +
> + return sprintf(buf, "%s\n", uacce->algs);
> +}
> +
...


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