Date:   Wed, 23 Jan 2019 14:28:28 +0200
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Oded Gabbay <oded.gabbay@...il.com>
Cc:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        ogabbay@...ana.ai
Subject: Re: [PATCH 05/15] habanalabs: add command buffer module

On Wed, Jan 23, 2019 at 02:00:47AM +0200, Oded Gabbay wrote:
> This patch adds the CB module, which allows the user to create and
> destroy CBs and to map them to the user's process address-space.

Can you please spell "command buffer" at least first time it's mentioned?
 
> A command buffer is a memory blocks that reside in DMA-able address-space
> and is physically contiguous so it can be accessed by the device without
> MMU translation. The command buffer memory is allocated using the
> coherent DMA API.
> 
> When creating a new CB, the IOCTL returns a handle of it, and the
> user-space process needs to use that handle to mmap the buffer to get a VA
> in the user's address-space.
> 
> Before destroying (freeing) a CB, the user must unmap the CB's VA using the
> CB handle.
> 
> Each CB has a reference counter, which tracks its usage in command
> submissions and also its mmaps (only a single mmap is allowed).
> 
> The driver maintains a pool of pre-allocated CBs in order to reduce
> latency during command submissions. In case the pool is empty, the driver
> will go to the slow-path of allocating a new CB, i.e. calling
> dma_alloc_coherent.
> 
> Signed-off-by: Oded Gabbay <oded.gabbay@...il.com>
> ---
>  drivers/misc/habanalabs/Makefile           |   3 +-
>  drivers/misc/habanalabs/command_buffer.c   | 414 +++++++++++++++++++++
>  drivers/misc/habanalabs/device.c           |  43 ++-
>  drivers/misc/habanalabs/goya/goya.c        |  28 ++
>  drivers/misc/habanalabs/habanalabs.h       |  95 ++++-
>  drivers/misc/habanalabs/habanalabs_drv.c   |   2 +
>  drivers/misc/habanalabs/habanalabs_ioctl.c | 102 +++++
>  include/uapi/misc/habanalabs.h             |  62 +++
>  8 files changed, 746 insertions(+), 3 deletions(-)
>  create mode 100644 drivers/misc/habanalabs/command_buffer.c
>  create mode 100644 drivers/misc/habanalabs/habanalabs_ioctl.c
>  create mode 100644 include/uapi/misc/habanalabs.h
> 
> diff --git a/drivers/misc/habanalabs/Makefile b/drivers/misc/habanalabs/Makefile
> index 3ffbadc2ca01..2530c9b78ca4 100644
> --- a/drivers/misc/habanalabs/Makefile
> +++ b/drivers/misc/habanalabs/Makefile
> @@ -4,7 +4,8 @@
>  
>  obj-m	:= habanalabs.o
>  
> -habanalabs-y := habanalabs_drv.o device.o context.o asid.o
> +habanalabs-y := habanalabs_drv.o device.o context.o asid.o habanalabs_ioctl.o \
> +		command_buffer.o
>  
>  include $(src)/goya/Makefile
>  habanalabs-y += $(HL_GOYA_FILES)
> diff --git a/drivers/misc/habanalabs/command_buffer.c b/drivers/misc/habanalabs/command_buffer.c
> new file mode 100644
> index 000000000000..535ed6cc5bda
> --- /dev/null
> +++ b/drivers/misc/habanalabs/command_buffer.c
> @@ -0,0 +1,414 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Copyright 2016-2018 HabanaLabs, Ltd.
> + * All Rights Reserved.
> + */
> +
> +#include <uapi/misc/habanalabs.h>
> +#include "habanalabs.h"
> +
> +#include <linux/dma-mapping.h>
> +
> +static void cb_fini(struct hl_device *hdev, struct hl_cb *cb)
> +{
> +	hdev->asic_funcs->dma_free_coherent(hdev, cb->size,
> +			(void *) cb->kernel_address, cb->bus_address);

As it seems, ASIC specific dma_free_coherent is a shortcut for a generic
dma_free_coherent. Why not use it directly?

> +	kfree(cb);
> +}
> +
> +static void cb_do_release(struct hl_device *hdev, struct hl_cb *cb)
> +{
> +	if (cb->is_pool) {
> +		spin_lock(&hdev->cb_pool_lock);
> +		list_add(&cb->pool_list, &hdev->cb_pool);
> +		spin_unlock(&hdev->cb_pool_lock);
> +	} else {
> +		cb_fini(hdev, cb);
> +	}
> +}
> +
> +static void cb_release(struct kref *ref)
> +{
> +	struct hl_device *hdev;
> +	struct hl_cb *cb;
> +
> +	cb = container_of(ref, struct hl_cb, refcount);
> +	hdev = cb->hdev;
> +
> +	cb_do_release(hdev, cb);
> +}
> +
> +static struct hl_cb *hl_cb_alloc(struct hl_device *hdev, u32 cb_size,
> +					int ctx_id)
> +{
> +	struct hl_cb *cb;
> +	void *p;
> +
> +	if (ctx_id == HL_KERNEL_ASID_ID)
> +		cb = kzalloc(sizeof(*cb), GFP_ATOMIC);

The GFP_ATOMIC should be used when the caller cannot tolerate reclaim or
sleep and it does not seem to be the case here.

> +	else
> +		cb = kzalloc(sizeof(*cb), GFP_KERNEL);
> +
> +	if (!cb)
> +		return NULL;
> +
> +	if (ctx_id == HL_KERNEL_ASID_ID)
> +		p = hdev->asic_funcs->dma_alloc_coherent(hdev, cb_size,
> +						&cb->bus_address, GFP_ATOMIC);

GFP_KERNEL?

> +	else
> +		p = hdev->asic_funcs->dma_alloc_coherent(hdev, cb_size,
> +						&cb->bus_address,
> +						GFP_USER | __GFP_ZERO);
> +	if (!p) {
> +		dev_err(hdev->dev,
> +			"failed to allocate %d of dma memory for CB\n",
> +			cb_size);
> +		kfree(cb);
> +		return NULL;
> +	}
> +
> +	cb->kernel_address = (u64) p;
> +	cb->size = cb_size;
> +
> +	return cb;
> +}
> +
> +int hl_cb_create(struct hl_device *hdev, struct hl_cb_mgr *mgr,
> +			u32 cb_size, u64 *handle, int ctx_id)
> +{
> +	struct hl_cb *cb;
> +	bool alloc_new_cb = true;
> +	int rc;
> +
> +	if (hdev->disabled) {
> +		dev_warn_ratelimited(hdev->dev,
> +			"Device is disabled !!! Can't create new CBs\n");
> +		rc = -EBUSY;
> +		goto out_err;
> +	}
> +
> +	/* Minimum allocation must be PAGE SIZE */
> +	if (cb_size < PAGE_SIZE)
> +		cb_size = PAGE_SIZE;
> +
> +	if (ctx_id == HL_KERNEL_ASID_ID &&
> +			cb_size <= hdev->asic_prop.cb_pool_cb_size) {
> +
> +		spin_lock(&hdev->cb_pool_lock);
> +		if (!list_empty(&hdev->cb_pool)) {
> +			cb = list_first_entry(&hdev->cb_pool, typeof(*cb),
> +					pool_list);
> +			list_del(&cb->pool_list);
> +			spin_unlock(&hdev->cb_pool_lock);
> +			alloc_new_cb = false;
> +		} else {
> +			spin_unlock(&hdev->cb_pool_lock);
> +			dev_warn_once(hdev->dev, "CB pool is empty\n");

Isn't it going to be a false alarm when you allocate the cb for the first
time?

> +		}
> +	}
> +
> +	if (alloc_new_cb) {
> +		cb = hl_cb_alloc(hdev, cb_size, ctx_id);
> +		if (!cb) {
> +			rc = -ENOMEM;
> +			goto out_err;
> +		}
> +	}
> +
> +	cb->hdev = hdev;
> +	cb->ctx_id = ctx_id;
> +
> +	spin_lock(&mgr->cb_lock);
> +	rc = idr_alloc(&mgr->cb_handles, cb, 1, 0, GFP_ATOMIC);

It seems the ID will remain dangling if the cb is reused.

> +	spin_unlock(&mgr->cb_lock);
> +
> +	if (rc < 0) {
> +		dev_err(hdev->dev, "Failed to allocate IDR for a new CB\n");
> +		goto release_cb;
> +	}
> +
> +	cb->id = rc;
> +
> +	kref_init(&cb->refcount);
> +	spin_lock_init(&cb->lock);
> +
> +	/*
> +	 * idr is 32-bit so we can safely OR it with a mask that is above
> +	 * 32 bit
> +	 */
> +	*handle = cb->id | HL_MMAP_CB_MASK;
> +	*handle <<= PAGE_SHIFT;
> +
> +	return 0;
> +
> +release_cb:
> +	cb_do_release(hdev, cb);
> +out_err:
> +	*handle = 0;
> +
> +	return rc;
> +}
> +
> +int hl_cb_destroy(struct hl_device *hdev, struct hl_cb_mgr *mgr, u64 cb_handle)
> +{
> +	struct hl_cb *cb;
> +	u32 handle;
> +	int rc = 0;
> +
> +	/*
> +	 * handle was given to user to do mmap, I need to shift it back to
> +	 * how the idr module gave it to me
> +	 */
> +	cb_handle >>= PAGE_SHIFT;
> +	handle = (u32) cb_handle;
> +
> +	spin_lock(&mgr->cb_lock);
> +
> +	cb = idr_find(&mgr->cb_handles, handle);
> +	if (cb) {
> +		idr_remove(&mgr->cb_handles, handle);
> +		spin_unlock(&mgr->cb_lock);
> +		kref_put(&cb->refcount, cb_release);
> +	} else {
> +		spin_unlock(&mgr->cb_lock);
> +		dev_err(hdev->dev,
> +			"CB destroy failed, no match to handle 0x%x\n", handle);
> +		rc = -EINVAL;
> +	}
> +
> +	return rc;
> +}
> +
> +int hl_cb_ioctl(struct hl_fpriv *hpriv, void *data)
> +{
> +	union hl_cb_args *args = data;
> +	struct hl_device *hdev = hpriv->hdev;
> +	u64 handle;
> +	int rc;
> +
> +	switch (args->in.op) {
> +	case HL_CB_OP_CREATE:
> +		rc = hl_cb_create(hdev, &hpriv->cb_mgr, args->in.cb_size,
> +					&handle, hpriv->ctx->asid);
> +		memset(args, 0, sizeof(*args));
> +		args->out.cb_handle = handle;
> +		break;
> +	case HL_CB_OP_DESTROY:
> +		rc = hl_cb_destroy(hdev, &hpriv->cb_mgr,
> +					args->in.cb_handle);
> +		memset(args, 0, sizeof(*args));
> +		break;
> +	default:
> +		rc = -EINVAL;
> +		break;
> +	}
> +
> +	return rc;
> +}
> +
> +static void cb_vm_close(struct vm_area_struct *vma)
> +{
> +	struct hl_cb *cb = (struct hl_cb *) vma->vm_private_data;
> +
> +	hl_cb_put(cb);
> +
> +	spin_lock(&cb->lock);
> +	cb->mmap = false;
> +	cb->vm_start = 0;
> +	cb->vm_end = 0;
> +	spin_unlock(&cb->lock);
> +
> +	vma->vm_private_data = NULL;
> +}
> +
> +static const struct vm_operations_struct cb_vm_ops = {
> +	.close = cb_vm_close
> +};
> +
> +int hl_cb_mmap(struct hl_fpriv *hpriv, struct vm_area_struct *vma)
> +{
> +	struct hl_device *hdev = hpriv->hdev;
> +	struct hl_cb *cb;
> +	phys_addr_t address;
> +	u32 handle;
> +	int rc;
> +
> +	handle = vma->vm_pgoff;
> +
> +	/* reference was taken here */
> +	cb = hl_cb_get(hdev, &hpriv->cb_mgr, handle);
> +	if (!cb) {
> +		dev_err(hdev->dev,
> +			"CB mmap failed, no match to handle %d\n", handle);
> +		goto err_out;

why no simply return -EINVAL?

> +	}
> +
> +	/* Validation check */
> +	if (vma->vm_end - vma->vm_start != cb->size) {
> +		dev_err(hdev->dev,
> +			"CB mmap failed, mmap size 0x%lx != 0x%x cb size\n",
> +			vma->vm_end - vma->vm_start, cb->size);
> +		goto put_cb;
> +	}
> +
> +	spin_lock(&cb->lock);
> +
> +	if (cb->mmap) {
> +		dev_err(hdev->dev,
> +			"CB mmap failed, CB already mmaped to user\n");
> +		goto release_lock;
> +	}
> +
> +	cb->mmap = true;
> +
> +	spin_unlock(&cb->lock);
> +
> +	vma->vm_ops = &cb_vm_ops;
> +
> +	/*
> +	 * Note: We're transferring the cb reference to
> +	 * vma->vm_private_data here.
> +	 */
> +
> +	vma->vm_private_data = cb;
> +
> +	/* Calculate address for CB */
> +	address = virt_to_phys((void *) cb->kernel_address);
> +
> +	rc = hdev->asic_funcs->cb_mmap(hdev, vma, cb->kernel_address,
> +					address, cb->size);
> +
> +	if (rc) {
> +		spin_lock(&cb->lock);
> +		cb->mmap = false;
> +		goto release_lock;
> +	}
> +
> +	cb->vm_start = vma->vm_start;
> +	cb->vm_end = vma->vm_end;
> +
> +	return 0;
> +
> +release_lock:
> +	spin_unlock(&cb->lock);
> +put_cb:
> +	hl_cb_put(cb);
> +err_out:
> +	return -EINVAL;
> +}
> +
> +struct hl_cb *hl_cb_get(struct hl_device *hdev, struct hl_cb_mgr *mgr,
> +			u32 handle)
> +{
> +	struct hl_cb *cb;
> +
> +	spin_lock(&mgr->cb_lock);
> +	cb = idr_find(&mgr->cb_handles, handle);
> +
> +	if (!cb) {
> +		spin_unlock(&mgr->cb_lock);
> +		dev_warn(hdev->dev,
> +			"CB get failed, no match to handle %d\n", handle);
> +		return NULL;
> +	}
> +
> +	kref_get(&cb->refcount);
> +
> +	spin_unlock(&mgr->cb_lock);
> +
> +	return cb;
> +
> +}
> +
> +void hl_cb_put(struct hl_cb *cb)
> +{
> +	kref_put(&cb->refcount, cb_release);
> +}
> +
> +void hl_cb_mgr_init(struct hl_cb_mgr *mgr)
> +{
> +	spin_lock_init(&mgr->cb_lock);
> +	idr_init(&mgr->cb_handles);
> +}
> +
> +void hl_cb_mgr_fini(struct hl_device *hdev, struct hl_cb_mgr *mgr)
> +{
> +	struct hl_cb *cb;
> +	struct idr *idp;
> +	u32 id;
> +
> +	idp = &mgr->cb_handles;
> +
> +	idr_for_each_entry(idp, cb, id) {
> +		if (kref_put(&cb->refcount, cb_release) != 1)
> +			dev_err(hdev->dev,
> +				"CB %d for CTX ID %d is still alive\n",
> +				id, cb->ctx_id);
> +	}
> +
> +	idr_destroy(&mgr->cb_handles);
> +}
> +
> +struct hl_cb *hl_cb_kernel_create(struct hl_device *hdev, u32 cb_size)
> +{
> +	u64 cb_handle;
> +	struct hl_cb *cb;
> +	int rc;
> +
> +	rc = hl_cb_create(hdev, &hdev->kernel_cb_mgr, cb_size, &cb_handle,
> +			HL_KERNEL_ASID_ID);
> +	if (rc) {
> +		dev_err(hdev->dev, "Failed to allocate CB for KMD %d\n", rc);
> +		return NULL;
> +	}
> +
> +	cb_handle >>= PAGE_SHIFT;
> +	cb = hl_cb_get(hdev, &hdev->kernel_cb_mgr, (u32) cb_handle);
> +	/* hl_cb_get should never fail here so use kernel WARN */
> +	WARN(!cb, "Kernel CB handle invalid 0x%x\n", (u32) cb_handle);
> +	if (!cb)
> +		goto destroy_cb;
> +
> +	return cb;
> +
> +destroy_cb:
> +	hl_cb_destroy(hdev, &hdev->kernel_cb_mgr, cb_handle << PAGE_SHIFT);
> +
> +	return NULL;
> +}
> +
> +int hl_cb_pool_init(struct hl_device *hdev)
> +{
> +	struct hl_cb *cb;
> +	int i;
> +
> +	INIT_LIST_HEAD(&hdev->cb_pool);
> +	spin_lock_init(&hdev->cb_pool_lock);
> +
> +	for (i = 0 ; i < hdev->asic_prop.cb_pool_cb_cnt ; i++) {
> +		cb = hl_cb_alloc(hdev, hdev->asic_prop.cb_pool_cb_size,
> +				HL_KERNEL_ASID_ID);
> +		if (cb) {
> +			cb->is_pool = true;
> +			list_add(&cb->pool_list, &hdev->cb_pool);
> +		} else {
> +			hl_cb_pool_fini(hdev);
> +			return -ENOMEM;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +int hl_cb_pool_fini(struct hl_device *hdev)
> +{
> +	struct hl_cb *cb, *tmp;
> +
> +	list_for_each_entry_safe(cb, tmp, &hdev->cb_pool, pool_list) {
> +		list_del(&cb->pool_list);
> +		cb_fini(hdev, cb);
> +	}
> +
> +	return 0;
> +}
> diff --git a/drivers/misc/habanalabs/device.c b/drivers/misc/habanalabs/device.c
> index 84ce9fcb52da..0bd86a7d34db 100644
> --- a/drivers/misc/habanalabs/device.c
> +++ b/drivers/misc/habanalabs/device.c
> @@ -53,6 +53,7 @@ static int hl_device_release(struct inode *inode, struct file *filp)
>  {
>  	struct hl_fpriv *hpriv = filp->private_data;
>  
> +	hl_cb_mgr_fini(hpriv->hdev, &hpriv->cb_mgr);
>  	hl_ctx_mgr_fini(hpriv->hdev, &hpriv->ctx_mgr);
>  
>  	filp->private_data = NULL;
> @@ -62,10 +63,34 @@ static int hl_device_release(struct inode *inode, struct file *filp)
>  	return 0;
>  }
>  
> +/**
> + * hl_mmap - mmap function for habanalabs device
> + *
> + * @*filp: pointer to file structure
> + * @*vma: pointer to vm_area_struct of the process
> + *
> + * Called when process does an mmap on habanalabs device. Call the device's mmap
> + * function at the end of the common code.
> + */
> +static int hl_mmap(struct file *filp, struct vm_area_struct *vma)
> +{
> +	struct hl_fpriv *hpriv = filp->private_data;
> +
> +	if ((vma->vm_pgoff & HL_MMAP_CB_MASK) == HL_MMAP_CB_MASK) {
> +		vma->vm_pgoff ^= HL_MMAP_CB_MASK;
> +		return hl_cb_mmap(hpriv, vma);
> +	}
> +
> +	return hpriv->hdev->asic_funcs->mmap(hpriv, vma);
> +}
> +
>  static const struct file_operations hl_ops = {
>  	.owner = THIS_MODULE,
>  	.open = hl_device_open,
> -	.release = hl_device_release
> +	.release = hl_device_release,
> +	.mmap = hl_mmap,
> +	.unlocked_ioctl = hl_ioctl,
> +	.compat_ioctl = hl_ioctl
>  };
>  
>  /**
> @@ -145,6 +170,8 @@ static int device_early_init(struct hl_device *hdev)
>  	if (rc)
>  		goto early_fini;
>  
> +	hl_cb_mgr_init(&hdev->kernel_cb_mgr);
> +
>  	mutex_init(&hdev->device_open);
>  	atomic_set(&hdev->fd_open_cnt, 0);
>  
> @@ -166,6 +193,8 @@ static int device_early_init(struct hl_device *hdev)
>  static void device_early_fini(struct hl_device *hdev)
>  {
>  
> +	hl_cb_mgr_fini(hdev, &hdev->kernel_cb_mgr);
> +
>  	hl_asid_fini(hdev);
>  
>  	if (hdev->asic_funcs->early_fini)
> @@ -280,11 +309,21 @@ int hl_device_init(struct hl_device *hdev, struct class *hclass)
>  		goto free_ctx;
>  	}
>  
> +	rc = hl_cb_pool_init(hdev);
> +	if (rc) {
> +		dev_err(hdev->dev, "failed to initialize CB pool\n");
> +		goto release_ctx;
> +	}
> +
>  	dev_notice(hdev->dev,
>  		"Successfully added device to habanalabs driver\n");
>  
>  	return 0;
>  
> +release_ctx:
> +	if (hl_ctx_put(hdev->kernel_ctx) != 1)
> +		dev_err(hdev->dev,
> +			"kernel ctx is still alive on initialization failure\n");
>  free_ctx:
>  	kfree(hdev->kernel_ctx);
>  sw_fini:
> @@ -321,6 +360,8 @@ void hl_device_fini(struct hl_device *hdev)
>  	/* Mark device as disabled */
>  	hdev->disabled = true;
>  
> +	hl_cb_pool_fini(hdev);
> +
>  	/* Release kernel context */
>  	if ((hdev->kernel_ctx) && (hl_ctx_put(hdev->kernel_ctx) != 1))
>  		dev_err(hdev->dev, "kernel ctx is still alive\n");
> diff --git a/drivers/misc/habanalabs/goya/goya.c b/drivers/misc/habanalabs/goya/goya.c
> index b2952296b890..341ac085af82 100644
> --- a/drivers/misc/habanalabs/goya/goya.c
> +++ b/drivers/misc/habanalabs/goya/goya.c
> @@ -92,6 +92,9 @@
>  
>  #define GOYA_MAX_INITIATORS		20
>  
> +#define GOYA_CB_POOL_CB_CNT		512
> +#define GOYA_CB_POOL_CB_SIZE		0x20000		/* 128KB */
> +
>  static void goya_get_fixed_properties(struct hl_device *hdev)
>  {
>  	struct asic_fixed_properties *prop = &hdev->asic_prop;
> @@ -119,6 +122,8 @@ static void goya_get_fixed_properties(struct hl_device *hdev)
>  	prop->tpc_enabled_mask = TPC_ENABLED_MASK;
>  
>  	prop->high_pll = PLL_HIGH_DEFAULT;
> +	prop->cb_pool_cb_cnt = GOYA_CB_POOL_CB_CNT;
> +	prop->cb_pool_cb_size = GOYA_CB_POOL_CB_SIZE;
>  }
>  
>  /**
> @@ -598,6 +603,27 @@ int goya_resume(struct hl_device *hdev)
>  	return 0;
>  }
>  
> +int goya_mmap(struct hl_fpriv *hpriv, struct vm_area_struct *vma)
> +{
> +	return -EINVAL;
> +}
> +
> +int goya_cb_mmap(struct hl_device *hdev, struct vm_area_struct *vma,
> +		u64 kaddress, phys_addr_t paddress, u32 size)
> +{
> +	int rc;
> +
> +	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP |
> +			VM_DONTCOPY | VM_NORESERVE;
> +
> +	rc = remap_pfn_range(vma, vma->vm_start, paddress >> PAGE_SHIFT,
> +				size, vma->vm_page_prot);
> +	if (rc)
> +		dev_err(hdev->dev, "remap_pfn_range error %d", rc);
> +
> +	return rc;
> +}
> +
>  void *goya_dma_alloc_coherent(struct hl_device *hdev, size_t size,
>  					dma_addr_t *dma_handle, gfp_t flags)
>  {
> @@ -617,6 +643,8 @@ static const struct hl_asic_funcs goya_funcs = {
>  	.sw_fini = goya_sw_fini,
>  	.suspend = goya_suspend,
>  	.resume = goya_resume,
> +	.mmap = goya_mmap,
> +	.cb_mmap = goya_cb_mmap,
>  	.dma_alloc_coherent = goya_dma_alloc_coherent,
>  	.dma_free_coherent = goya_dma_free_coherent,
>  };
> diff --git a/drivers/misc/habanalabs/habanalabs.h b/drivers/misc/habanalabs/habanalabs.h
> index d003a6af2131..6ad476df65b0 100644
> --- a/drivers/misc/habanalabs/habanalabs.h
> +++ b/drivers/misc/habanalabs/habanalabs.h
> @@ -21,10 +21,12 @@
>  
>  #define HL_NAME				"habanalabs"
>  
> +#define HL_MMAP_CB_MASK			(0x8000000000000000ull >> PAGE_SHIFT)
> +
>  #define HL_MAX_QUEUES			128
>  
>  struct hl_device;
> -
> +struct hl_fpriv;
>  
>  
>  
> @@ -53,6 +55,8 @@ struct hl_device;
>   * @max_asid: maximum number of open contexts (ASIDs).
>   * @completion_queues_count: number of completion queues.
>   * @high_pll: high PLL frequency used by the device.
> + * @cb_pool_cb_cnt: number of CBs in the CB pool.
> + * @cb_pool_cb_size: size of each CB in the CB pool.
>   * @tpc_enabled_mask: which TPCs are enabled.
>   */
>  struct asic_fixed_properties {
> @@ -73,11 +77,68 @@ struct asic_fixed_properties {
>  	u32			sram_size;
>  	u32			max_asid;
>  	u32			high_pll;
> +	u32			cb_pool_cb_cnt;
> +	u32			cb_pool_cb_size;
>  	u8			completion_queues_count;
>  	u8			tpc_enabled_mask;
>  };
>  
>  
> +
> +
> +
> +
> +/*
> + * Command Buffers
> + */
> +
> +/**
> + * struct hl_cb_mgr - describes a Command Buffer Manager.
> + * @cb_lock: protects cb_handles.
> + * @cb_handles: an idr to hold all command buffer handles.
> + */
> +struct hl_cb_mgr {
> +	spinlock_t		cb_lock;
> +	struct idr		cb_handles; /* protected by cb_lock */
> +};
> +
> +/**
> + * struct hl_cb - describes a Command Buffer.
> + * @refcount: reference counter for usage of the CB.
> + * @hdev: pointer to device this CB belongs to.
> + * @lock: spinlock to protect mmap/cs flows.
> + * @pool_list: node in pool list of command buffers.
> + * @kernel_address: Holds the CB's kernel virtual address.
> + * @bus_address: Holds the CB's DMA address.
> + * @vm_start: Holds the CB's user start virtual address (when mmaped).
> + * @vm_end: Holds the CB's user end virtual address (when mmaped).
> + * @size: holds the CB's size.
> + * @id: the CB's ID.
> + * @ctx_id: holds the ID of the owner's context.
> + * @mmap: true if the CB is currently mmaped to user.
> + * @is_pool: true if CB was acquired from the pool, false otherwise.
> + */
> +struct hl_cb {
> +	struct kref		refcount;
> +	struct hl_device	*hdev;
> +	spinlock_t		lock;
> +	struct list_head	pool_list;
> +	u64			kernel_address;
> +	dma_addr_t		bus_address;
> +	u64			vm_start;
> +	u64			vm_end;
> +	u32			size;
> +	u32			id;
> +	u32			ctx_id;
> +	u8			mmap;
> +	u8			is_pool;
> +};
> +
> +
> +
> +
> +
> +
>  #define HL_QUEUE_LENGTH			256
>  
>  
> @@ -109,6 +170,8 @@ enum hl_asic_type {
>   * @sw_fini: tears down driver state, does not configure H/W.
>   * @suspend: handles IP specific H/W or SW changes for suspend.
>   * @resume: handles IP specific H/W or SW changes for resume.
> + * @mmap: mmap function, does nothing.
> + * @cb_mmap: maps a CB.
>   * @dma_alloc_coherent: DMA allocate coherent memory.
>   * @dma_free_coherent: free DMA allocation.
>   */
> @@ -119,6 +182,9 @@ struct hl_asic_funcs {
>  	int (*sw_fini)(struct hl_device *hdev);
>  	int (*suspend)(struct hl_device *hdev);
>  	int (*resume)(struct hl_device *hdev);
> +	int (*mmap)(struct hl_fpriv *hpriv, struct vm_area_struct *vma);
> +	int (*cb_mmap)(struct hl_device *hdev, struct vm_area_struct *vma,
> +			u64 kaddress, phys_addr_t paddress, u32 size);
>  	void* (*dma_alloc_coherent)(struct hl_device *hdev, size_t size,
>  					dma_addr_t *dma_handle, gfp_t flag);
>  	void (*dma_free_coherent)(struct hl_device *hdev, size_t size,
> @@ -175,6 +241,7 @@ struct hl_ctx_mgr {
>   * @taskpid: current process ID.
>   * @ctx: current executing context.
>   * @ctx_mgr: context manager to handle multiple context for this FD.
> + * @cb_mgr: command buffer manager to handle multiple buffers for this FD.
>   * @refcount: number of related contexts.
>   */
>  struct hl_fpriv {
> @@ -183,6 +250,7 @@ struct hl_fpriv {
>  	struct pid		*taskpid;
>  	struct hl_ctx		*ctx; /* TODO: remove for multiple ctx */
>  	struct hl_ctx_mgr	ctx_mgr;
> +	struct hl_cb_mgr	cb_mgr;
>  	struct kref		refcount;
>  };
>  
> @@ -239,6 +307,7 @@ void hl_wreg(struct hl_device *hdev, u32 reg, u32 val);
>   * @asic_name: ASIC specific nmae.
>   * @asic_type: ASIC specific type.
>   * @kernel_ctx: KMD context structure.
> + * @kernel_cb_mgr: command buffer manager for creating/destroying/handling CGs.
>   * @dma_pool: DMA pool for small allocations.
>   * @cpu_accessible_dma_mem: KMD <-> ArmCP shared memory CPU address.
>   * @cpu_accessible_dma_address: KMD <-> ArmCP shared memory DMA address.
> @@ -249,6 +318,8 @@ void hl_wreg(struct hl_device *hdev, u32 reg, u32 val);
>   * @asic_prop: ASIC specific immutable properties.
>   * @asic_funcs: ASIC specific functions.
>   * @asic_specific: ASIC specific information to use only from ASIC files.
> + * @cb_pool: list of preallocated CBs.
> + * @cb_pool_lock: protects the CB pool.
>   * @user_ctx: current user context executing.
>   * @fd_open_cnt: number of open context executing.
>   * @major: habanalabs KMD major.
> @@ -264,6 +335,7 @@ struct hl_device {
>  	char				asic_name[16];
>  	enum hl_asic_type		asic_type;
>  	struct hl_ctx			*kernel_ctx;
> +	struct hl_cb_mgr		kernel_cb_mgr;
>  	struct dma_pool			*dma_pool;
>  	void				*cpu_accessible_dma_mem;
>  	dma_addr_t			cpu_accessible_dma_address;
> @@ -275,6 +347,10 @@ struct hl_device {
>  	struct asic_fixed_properties	asic_prop;
>  	const struct hl_asic_funcs	*asic_funcs;
>  	void				*asic_specific;
> +
> +	struct list_head		cb_pool;
> +	spinlock_t			cb_pool_lock;
> +
>  	/* TODO: The following fields should be moved for multi-context */
>  	struct hl_ctx			*user_ctx;
>  	atomic_t			fd_open_cnt;
> @@ -345,6 +421,23 @@ int hl_device_resume(struct hl_device *hdev);
>  void hl_hpriv_get(struct hl_fpriv *hpriv);
>  void hl_hpriv_put(struct hl_fpriv *hpriv);
>  
> +int hl_cb_create(struct hl_device *hdev, struct hl_cb_mgr *mgr, u32 cb_size,
> +		u64 *handle, int ctx_id);
> +int hl_cb_destroy(struct hl_device *hdev, struct hl_cb_mgr *mgr, u64 cb_handle);
> +int hl_cb_mmap(struct hl_fpriv *hpriv, struct vm_area_struct *vma);
> +struct hl_cb *hl_cb_get(struct hl_device *hdev,	struct hl_cb_mgr *mgr,
> +			u32 handle);
> +void hl_cb_put(struct hl_cb *cb);
> +void hl_cb_mgr_init(struct hl_cb_mgr *mgr);
> +void hl_cb_mgr_fini(struct hl_device *hdev, struct hl_cb_mgr *mgr);
> +struct hl_cb *hl_cb_kernel_create(struct hl_device *hdev, u32 cb_size);
> +int hl_cb_pool_init(struct hl_device *hdev);
> +int hl_cb_pool_fini(struct hl_device *hdev);
> +
>  void goya_set_asic_funcs(struct hl_device *hdev);
>  
> +/* IOCTLs */
> +long hl_ioctl(struct file *filep, unsigned int cmd, unsigned long arg);
> +int hl_cb_ioctl(struct hl_fpriv *hpriv, void *data);
> +
>  #endif /* HABANALABSP_H_ */
> diff --git a/drivers/misc/habanalabs/habanalabs_drv.c b/drivers/misc/habanalabs/habanalabs_drv.c
> index 0646da83eb53..5c312dd3aa50 100644
> --- a/drivers/misc/habanalabs/habanalabs_drv.c
> +++ b/drivers/misc/habanalabs/habanalabs_drv.c
> @@ -123,6 +123,7 @@ int hl_device_open(struct inode *inode, struct file *filp)
>  	kref_init(&hpriv->refcount);
>  	nonseekable_open(inode, filp);
>  
> +	hl_cb_mgr_init(&hpriv->cb_mgr);
>  	hl_ctx_mgr_init(&hpriv->ctx_mgr);
>  
>  	rc = hl_ctx_create(hdev, hpriv);
> @@ -138,6 +139,7 @@ int hl_device_open(struct inode *inode, struct file *filp)
>  out_err:
>  	filp->private_data = NULL;
>  	hl_ctx_mgr_fini(hpriv->hdev, &hpriv->ctx_mgr);
> +	hl_cb_mgr_fini(hpriv->hdev, &hpriv->cb_mgr);
>  	kfree(hpriv);
>  
>  close_device:
> diff --git a/drivers/misc/habanalabs/habanalabs_ioctl.c b/drivers/misc/habanalabs/habanalabs_ioctl.c
> new file mode 100644
> index 000000000000..fa2287569e0e
> --- /dev/null
> +++ b/drivers/misc/habanalabs/habanalabs_ioctl.c
> @@ -0,0 +1,102 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Copyright 2016-2018 HabanaLabs, Ltd.
> + * All Rights Reserved.
> + */
> +
> +#include <uapi/misc/habanalabs.h>
> +#include "habanalabs.h"
> +
> +#include <linux/fs.h>
> +#include <linux/uaccess.h>
> +#include <linux/cred.h>
> +
> +#define HL_IOCTL_DEF(ioctl, _func) \
> +	[_IOC_NR(ioctl)] = {.cmd = ioctl, .func = _func}
> +
> +static const struct hl_ioctl_desc hl_ioctls[] = {
> +	HL_IOCTL_DEF(HL_IOCTL_CB, hl_cb_ioctl)
> +};
> +
> +#define HL_CORE_IOCTL_COUNT	ARRAY_SIZE(hl_ioctls)
> +
> +long hl_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
> +{
> +	struct hl_fpriv *hpriv = filep->private_data;
> +	struct hl_device *hdev = hpriv->hdev;
> +	hl_ioctl_t *func;
> +	const struct hl_ioctl_desc *ioctl = NULL;
> +	unsigned int nr = _IOC_NR(cmd);
> +	char stack_kdata[128];
> +	char *kdata = NULL;
> +	unsigned int usize, asize;
> +	int retcode = -EINVAL;
> +
> +	if (nr >= HL_CORE_IOCTL_COUNT)

	nr > HL_CORE_IOCTL_COUNT, isn't it?

> +		goto err_i1;

err_i1 is not very meaningfull. Maybe invalid_ioctl?

> +
> +	if ((nr >= HL_COMMAND_START) && (nr < HL_COMMAND_END)) {

The HL_COMMAND_{START,END} do not seem to be defined. 
Besides, this check seem to be overlapped with

	if (nr > HL_CORE_IOCTL_COUNT)

> +		u32 hl_size;
> +
> +		ioctl = &hl_ioctls[nr];
> +
> +		hl_size = _IOC_SIZE(ioctl->cmd);
> +		usize = asize = _IOC_SIZE(cmd);
> +		if (hl_size > asize)
> +			asize = hl_size;
> +
> +		cmd = ioctl->cmd;
> +	} else {
> +		goto err_i1;
> +	}
> +
> +	/* Do not trust userspace, use our own definition */
> +	func = ioctl->func;
> +
> +	if (unlikely(!func)) {
> +		dev_dbg(hdev->dev, "no function\n");
> +		retcode = -EINVAL;
> +		goto err_i1;
> +	}
> +
> +	if (cmd & (IOC_IN | IOC_OUT)) {
> +		if (asize <= sizeof(stack_kdata)) {
> +			kdata = stack_kdata;
> +		} else {
> +			kdata = kmalloc(asize, GFP_KERNEL);
> +			if (!kdata) {
> +				retcode = -ENOMEM;
> +				goto err_i1;
> +			}
> +		}
> +		if (asize > usize)
> +			memset(kdata + usize, 0, asize - usize);

Just init stack_kdata to 0 and use kzalloc instead of malloc.

> +	}
> +
> +	if (cmd & IOC_IN) {
> +		if (copy_from_user(kdata, (void __user *)arg, usize)) {
> +			retcode = -EFAULT;
> +			goto err_i1;
> +		}
> +	} else if (cmd & IOC_OUT) {
> +		memset(kdata, 0, usize);
> +	}
> +
> +	retcode = func(hpriv, kdata);
> +
> +	if (cmd & IOC_OUT)
> +		if (copy_to_user((void __user *)arg, kdata, usize))
> +			retcode = -EFAULT;
> +
> +err_i1:
> +	if (!ioctl)
> +		dev_dbg(hdev->dev,
> +			"invalid ioctl: pid=%d, cmd=0x%02x, nr=0x%02x\n",
> +			  task_pid_nr(current), cmd, nr);

I think this can move right after the 'nr' sanity check and there you can
simple return -EINVAL after dev_dbg().

> +
> +	if (kdata != stack_kdata)
> +		kfree(kdata);
> +
> +	return retcode;
> +}
> diff --git a/include/uapi/misc/habanalabs.h b/include/uapi/misc/habanalabs.h
> new file mode 100644
> index 000000000000..b3f9213d4709
> --- /dev/null
> +++ b/include/uapi/misc/habanalabs.h
> @@ -0,0 +1,62 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
> + *
> + * Copyright 2016-2018 HabanaLabs, Ltd.
> + * All Rights Reserved.
> + *
> + * Author: Oded Gabbay <oded.gabbay@...il.com>
> + *
> + */
> +
> +#ifndef HABANALABS_H_
> +#define HABANALABS_H_
> +
> +#include <linux/types.h>
> +#include <linux/ioctl.h>
> +
> +/* Opcode to create a new command buffer */
> +#define HL_CB_OP_CREATE		0
> +/* Opcode to destroy previously created command buffer */
> +#define HL_CB_OP_DESTROY	1
> +
> +struct hl_cb_in {
> +	/* Handle of CB or 0 if we want to create one */
> +	__u64 cb_handle;
> +	/* HL_CB_OP_* */
> +	__u32 op;
> +	/* Size of CB. Minimum requested size must be PAGE_SIZE */
> +	__u32 cb_size;
> +	/* Context ID - Currently not in use */
> +	__u32 ctx_id;
> +	__u32 pad;
> +};
> +
> +struct hl_cb_out {
> +	/* Handle of CB */
> +	__u64 cb_handle;
> +};
> +
> +union hl_cb_args {
> +	struct hl_cb_in in;
> +	struct hl_cb_out out;
> +};
> +
> +/*
> + * Command Buffer
> + * - Request a Command Buffer
> + * - Destroy a Command Buffer
> + *
> + * The command buffers are memory blocks that reside in DMA-able address
> + * space and are physically contiguous so they can be accessed by the device
> + * directly. They are allocated using the coherent DMA API.
> + *
> + * When creating a new CB, the IOCTL returns a handle of it, and the user-space
> + * process needs to use that handle to mmap the buffer so it can access them.
> + *
> + */
> +#define HL_IOCTL_CB		\
> +		_IOWR('H', 0x02, union hl_cb_args)
> +
> +#define HL_COMMAND_START	0x02
> +#define HL_COMMAND_END		0x03
> +
> +#endif /* HABANALABS_H_ */
> -- 
> 2.17.1
> 

-- 
Sincerely yours,
Mike.

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