Re: [PATCH v10 2/4] uacce: add uacce driver

[Jonathan Cameron]

On Mon, 16 Dec 2019 11:08:15 +0800
Zhangfei Gao <zhangfei.gao@xxxxxxxxxx> wrote:

> From: Kenneth Lee <liguozhu@xxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxx>
> Signed-off-by: Zaibo Xu <xuzaibo@xxxxxxxxxx>
> Signed-off-by: Zhou Wang <wangzhou1@xxxxxxxxxxxxx>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> Signed-off-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxx>

Hi,

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

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>

> ---
>  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@xxxxxxxxxxxxxxxx
> +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);
> +}
> +
...