[PATCH 2/3] cxl: Introduce afu_desc sysfs attribute

[Andrew Donnellan]

On 14/03/17 15:06, Vaibhav Jain wrote:
> This patch introduces a new afu sysfs attribute named afu_desc. This
> binary attribute provides access to raw contents of the afu descriptor
> to user-space. Direct access to afu descriptor is useful for libcxl
> that can use it to determine if the CXL card has been fenced or
> provide application access to afu attributes beyond one defined in
> CAIA.
>
> We introduce three new backend-ops:
>
> * afu_desc_size(): Return the size in bytes of the afu descriptor.
>
> * afu_desc_read(): Copy into a provided buffer contents of afu
>   descriptor starting at specific offset.
>
> * afu_desc_mmap(): Memory map the afu descriptor to the given
>   vm_area_struct.
>
> If afu_desc_size() > 0 the afu_desc attribute gets created for the AFU.
> The bin_attribute callbacks route the calls to corresponding cxl backend
> implementation.
>
> Signed-off-by: Vaibhav Jain <vaibhav at linux.vnet.ibm.com>
> ---
>  Documentation/ABI/testing/sysfs-class-cxl |  9 +++++++
>  drivers/misc/cxl/cxl.h                    |  9 +++++++
>  drivers/misc/cxl/sysfs.c                  | 45 +++++++++++++++++++++++++++++++
>  3 files changed, 63 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-class-cxl b/Documentation/ABI/testing/sysfs-class-cxl
> index 640f65e..9ac84c4 100644
> --- a/Documentation/ABI/testing/sysfs-class-cxl
> +++ b/Documentation/ABI/testing/sysfs-class-cxl
> @@ -6,6 +6,15 @@ Example: The real path of the attribute /sys/class/cxl/afu0.0s/irqs_max is
>
>  Slave contexts (eg. /sys/class/cxl/afu0.0s):
>
> +What:           /sys/class/cxl/<afu>/afu_desc
> +Date:           March 2016
> +Contact:        linuxppc-dev at lists.ozlabs.org
> +Description:    read only
> +                AFU Descriptor contents. The contents of this file are
> +		binary contents of the AFU descriptor. LIBCXL library can

"The libcxl"

> +		use this file to read afu descriptor and in some special cases
> +		determine if the cxl card has been fenced.
> +
>  What:           /sys/class/cxl/<afu>/afu_err_buf
>  Date:           September 2014
>  Contact:        linuxppc-dev at lists.ozlabs.org
> diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
> index ef683b7..1c43d06 100644
> --- a/drivers/misc/cxl/cxl.h
> +++ b/drivers/misc/cxl/cxl.h
> @@ -426,6 +426,9 @@ struct cxl_afu {
>  	u64 eb_len, eb_offset;
>  	struct bin_attribute attr_eb;
>
> +	/* Afu descriptor */
> +	struct bin_attribute attr_afud;
> +
>  	/* pointer to the vphb */
>  	struct pci_controller *phb;
>
> @@ -995,6 +998,12 @@ struct cxl_backend_ops {
>  	int (*afu_cr_write16)(struct cxl_afu *afu, int cr_idx, u64 offset, u16 val);
>  	int (*afu_cr_write32)(struct cxl_afu *afu, int cr_idx, u64 offset, u32 val);
>  	ssize_t (*read_adapter_vpd)(struct cxl *adapter, void *buf, size_t count);
> +	/* Access to AFU descriptor */
> +	ssize_t (*afu_desc_size)(struct cxl_afu *afu);
> +	ssize_t (*afu_desc_read)(struct cxl_afu *afu, char *buf, loff_t off,
> +				 size_t count);
> +	int (*afu_desc_mmap)(struct cxl_afu *afu, struct file *filp,
> +			     struct vm_area_struct *vma);
>  };
>  extern const struct cxl_backend_ops cxl_native_ops;
>  extern const struct cxl_backend_ops cxl_guest_ops;
> diff --git a/drivers/misc/cxl/sysfs.c b/drivers/misc/cxl/sysfs.c
> index a8b6d6a..fff3468 100644
> --- a/drivers/misc/cxl/sysfs.c
> +++ b/drivers/misc/cxl/sysfs.c
> @@ -426,6 +426,26 @@ static ssize_t afu_eb_read(struct file *filp, struct kobject *kobj,
>  	return cxl_ops->afu_read_err_buffer(afu, buf, off, count);
>  }
>
> +static ssize_t afu_desc_read(struct file *filp, struct kobject *kobj,
> +			     struct bin_attribute *bin_attr, char *buf,
> +			     loff_t off, size_t count)
> +{
> +	struct cxl_afu *afu = to_cxl_afu(kobj_to_dev(kobj));
> +
> +	return cxl_ops->afu_desc_read ?
> +		cxl_ops->afu_desc_read(afu, buf, off, count) : -EIO;
> +}
> +
> +static int afu_desc_mmap(struct file *filp, struct kobject *kobj,
> +			 struct bin_attribute *attr, struct vm_area_struct *vma)
> +{
> +	struct cxl_afu *afu = to_cxl_afu(kobj_to_dev(kobj));
> +
> +	return cxl_ops->afu_desc_mmap ?
> +		cxl_ops->afu_desc_mmap(afu, filp, vma) : -EINVAL;
> +}
> +
> +
>  static struct device_attribute afu_attrs[] = {
>  	__ATTR_RO(mmio_size),
>  	__ATTR_RO(irqs_min),
> @@ -625,6 +645,9 @@ void cxl_sysfs_afu_remove(struct cxl_afu *afu)
>  	struct afu_config_record *cr, *tmp;
>  	int i;
>
> +	if (afu->attr_afud.size > 0)
> +		device_remove_bin_file(&afu->dev, &afu->attr_afud);
> +
>  	/* remove the err buffer bin attribute */
>  	if (afu->eb_len)
>  		device_remove_bin_file(&afu->dev, &afu->attr_eb);
> @@ -686,6 +709,28 @@ int cxl_sysfs_afu_add(struct cxl_afu *afu)
>  		list_add(&cr->list, &afu->crs);
>  	}
>
> +	/* Create the sysfs binattr for afu-descriptor */
> +	afu->attr_afud.size = cxl_ops->afu_desc_size ?
> +		cxl_ops->afu_desc_size(afu) : 0;
> +
> +	if (afu->attr_afud.size > 0) {
> +		sysfs_attr_init(&afu->attr_afud.attr);
> +		afu->attr_afud.attr.name = "afu_desc";
> +		afu->attr_afud.attr.mode = 0444;

Per Fred, I'm not convinced that 444 is completely safe.

> +		afu->attr_afud.read = afu_desc_read;
> +		afu->attr_afud.mmap = afu_desc_mmap;
> +
> +		rc = device_create_bin_file(&afu->dev, &afu->attr_afud);
> +		if (rc) {
> +			/* indicate that we did'nt create the sysfs attr */

didn't

> +			afu->attr_afud.size = 0;
> +			dev_err(&afu->dev,
> +				"Unable to create afu_desc attr for the afu. Err(%d)\n",
> +				rc);
> +			goto err1;
> +		}
> +	}
> +
>  	return 0;
>
>  err1:
>

-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan at au1.ibm.com  IBM Australia Limited