Re: [PATCH 12/83] hsa/radeon: Add kfd mmap handler

[Jerome Glisse]

On Fri, Jul 11, 2014 at 12:50:12AM +0300, Oded Gabbay wrote:
> This patch adds the kfd mmap handler that maps the physical address
> of a doorbell page to a user-space virtual address. That virtual address
> belongs to the process that uses the doorbell page.
> 
> This mmap handler is called only from within the kernel and not to be
> called from user-mode mmap of /dev/kfd.

I think you need to modify max doorbell to be function of page size.
You definitly want to forbid any access to other process doorbell and
you can only map page with PAGE_SIZE granularity hence you need to
modulate the max number of doorbell depending on page size and not
assume page size is 4k on x86. Someone might build a kernel with
different page size and if it wants to use this driver it will open
several security issues.

Cheers,
Jérôme

> 
> Signed-off-by: Oded Gabbay <oded.gabbay@xxxxxxx>
> ---
>  drivers/gpu/hsa/radeon/kfd_chardev.c  | 20 +++++++++
>  drivers/gpu/hsa/radeon/kfd_doorbell.c | 85 +++++++++++++++++++++++++++++++++++
>  2 files changed, 105 insertions(+)
> 
> diff --git a/drivers/gpu/hsa/radeon/kfd_chardev.c b/drivers/gpu/hsa/radeon/kfd_chardev.c
> index 7a56a8f..0b5bc74 100644
> --- a/drivers/gpu/hsa/radeon/kfd_chardev.c
> +++ b/drivers/gpu/hsa/radeon/kfd_chardev.c
> @@ -39,6 +39,7 @@ static const struct file_operations kfd_fops = {
>  	.owner = THIS_MODULE,
>  	.unlocked_ioctl = kfd_ioctl,
>  	.open = kfd_open,
> +	.mmap = kfd_mmap,
>  };
>  
>  static int kfd_char_dev_major = -1;
> @@ -131,3 +132,22 @@ kfd_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
>  
>  	return err;
>  }
> +
> +static int
> +kfd_mmap(struct file *filp, struct vm_area_struct *vma)
> +{
> +	unsigned long pgoff = vma->vm_pgoff;
> +	struct kfd_process *process;
> +
> +	process = radeon_kfd_get_process(current);
> +	if (IS_ERR(process))
> +		return PTR_ERR(process);
> +
> +	if (pgoff < KFD_MMAP_DOORBELL_START)
> +		return -EINVAL;
> +
> +	if (pgoff < KFD_MMAP_DOORBELL_END)
> +		return radeon_kfd_doorbell_mmap(process, vma);
> +
> +	return -EINVAL;
> +}
> diff --git a/drivers/gpu/hsa/radeon/kfd_doorbell.c b/drivers/gpu/hsa/radeon/kfd_doorbell.c
> index 79a9d4b..e1d8506 100644
> --- a/drivers/gpu/hsa/radeon/kfd_doorbell.c
> +++ b/drivers/gpu/hsa/radeon/kfd_doorbell.c
> @@ -70,3 +70,88 @@ void radeon_kfd_doorbell_init(struct kfd_dev *kfd)
>  	kfd->doorbell_process_limit = doorbell_process_limit;
>  }
>  
> +/* This is the /dev/kfd mmap (for doorbell) implementation. We intend that this is only called through map_doorbells,
> +** not through user-mode mmap of /dev/kfd. */
> +int radeon_kfd_doorbell_mmap(struct kfd_process *process, struct vm_area_struct *vma)
> +{
> +	unsigned int device_index;
> +	struct kfd_dev *dev;
> +	phys_addr_t start;
> +
> +	BUG_ON(vma->vm_pgoff < KFD_MMAP_DOORBELL_START || vma->vm_pgoff >= KFD_MMAP_DOORBELL_END);
> +
> +	/* For simplicitly we only allow mapping of the entire doorbell allocation of a single device & process. */
> +	if (vma->vm_end - vma->vm_start != doorbell_process_allocation())
> +		return -EINVAL;
> +
> +	/* device_index must be GPU ID!! */
> +	device_index = vma->vm_pgoff - KFD_MMAP_DOORBELL_START;
> +
> +	dev = radeon_kfd_device_by_id(device_index);
> +	if (dev == NULL)
> +		return -EINVAL;
> +
> +	vma->vm_flags |= VM_IO | VM_DONTCOPY | VM_DONTEXPAND | VM_NORESERVE | VM_DONTDUMP | VM_PFNMAP;
> +	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> +
> +	start = dev->doorbell_base + process->pasid * doorbell_process_allocation();
> +
> +	pr_debug("kfd: mapping doorbell page in radeon_kfd_doorbell_mmap\n"
> +		 "     target user address == 0x%016llX\n"
> +		 "     physical address    == 0x%016llX\n"
> +		 "     vm_flags            == 0x%08lX\n"
> +		 "     size                == 0x%08lX\n",
> +		 (long long unsigned int) vma->vm_start, start, vma->vm_flags,
> +		 doorbell_process_allocation());
> +
> +	return io_remap_pfn_range(vma,
> +				vma->vm_start,
> +				start >> PAGE_SHIFT,
> +				doorbell_process_allocation(),
> +				vma->vm_page_prot);
> +}
> +
> +/* Map the doorbells for a single process & device. This will indirectly call radeon_kfd_doorbell_mmap.
> +** This assumes that the process mutex is being held. */
> +static int
> +map_doorbells(struct file *devkfd, struct kfd_process *process, struct kfd_dev *dev)
> +{
> +	struct kfd_process_device *pdd = radeon_kfd_get_process_device_data(dev, process);
> +
> +	if (pdd == NULL)
> +		return -ENOMEM;
> +
> +	if (pdd->doorbell_mapping == NULL) {
> +		unsigned long offset = (KFD_MMAP_DOORBELL_START + dev->id) << PAGE_SHIFT;
> +		doorbell_t __user *doorbell_mapping;
> +
> +		doorbell_mapping = (doorbell_t __user *)vm_mmap(devkfd, 0, doorbell_process_allocation(), PROT_WRITE,
> +								MAP_SHARED, offset);
> +		if (IS_ERR(doorbell_mapping))
> +			return PTR_ERR(doorbell_mapping);
> +
> +		pdd->doorbell_mapping = doorbell_mapping;
> +	}
> +
> +	return 0;
> +}
> +
> +/* Get the user-mode address of a doorbell. Assumes that the process mutex is being held. */
> +doorbell_t __user *radeon_kfd_get_doorbell(struct file *devkfd, struct kfd_process *process, struct kfd_dev *dev,
> +					   unsigned int doorbell_index)
> +{
> +	struct kfd_process_device *pdd;
> +	int err;
> +
> +	BUG_ON(doorbell_index > MAX_DOORBELL_INDEX);
> +
> +	err = map_doorbells(devkfd, process, dev);
> +	if (err)
> +		return ERR_PTR(err);
> +
> +	pdd = radeon_kfd_get_process_device_data(dev, process);
> +	BUG_ON(pdd == NULL); /* map_doorbells would have failed otherwise */
> +
> +	return &pdd->doorbell_mapping[doorbell_index];
> +}
> +
> -- 
> 1.9.1
> 
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