Re: [PATCH v3 12/14] fs/configfs: Add a callback to determine attribute visibility

[Tom Lendacky <thomas.lendacky@amd.com>]

On 4/16/24 13:25, Dan Williams wrote:
> Tom Lendacky wrote:
>> On 4/16/24 00:46, Dan Williams wrote:
>>> Tom Lendacky wrote:
>>>> In order to support dynamic decisions as to whether an attribute should be
>>>> created, add a callback that returns a bool to indicate whether the
>>>> attribute should be display. If no callback is registered, the attribute
> [..]
>>>> Cc: Joel Becker <jlbec@evilplan.org>
>>>> Cc: Christoph Hellwig <hch@lst.de>
>>>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>>>> ---
>>>>    fs/configfs/file.c       |   7 +++
>>>>    include/linux/configfs.h | 111 +++++++++++++++++++++++++++------------
>>>>    2 files changed, 84 insertions(+), 34 deletions(-)
>>>>
> [..]
>>>> diff --git a/include/linux/configfs.h b/include/linux/configfs.h
>>>> index 2606711adb18..c836d7bc7c9e 100644
>>>> --- a/include/linux/configfs.h
>>>> +++ b/include/linux/configfs.h
>>>> @@ -116,35 +116,57 @@ struct configfs_attribute {
>>>>    	const char		*ca_name;
>>>>    	struct module 		*ca_owner;
>>>>    	umode_t			ca_mode;
>>>> +	bool (*is_visible)(const struct config_item *, const struct configfs_attribute *);
>>>>    	ssize_t (*show)(struct config_item *, char *);
>>>>    	ssize_t (*store)(struct config_item *, const char *, size_t);
>>>>    };
>>>>    
>>>> -#define CONFIGFS_ATTR(_pfx, _name)			\
>>>> +#define __CONFIGFS_ATTR(_pfx, _name, _vis)		\
>>>>    static struct configfs_attribute _pfx##attr_##_name = {	\
>>>>    	.ca_name	= __stringify(_name),		\
>>>>    	.ca_mode	= S_IRUGO | S_IWUSR,		\
>>>>    	.ca_owner	= THIS_MODULE,			\
>>>> +	.is_visible	= _vis,				\
>>>>    	.show		= _pfx##_name##_show,		\
>>>>    	.store		= _pfx##_name##_store,		\
>>>
>>> Shouldn't this operation live in configfs_group_operations? That would
>>> mirror the sysfs organization, and likely saves some memory.
>>
>> I suppose it can, but then you lose the grouping of attributes within
>> the same directory, right? A configfs group will result in moving the
>> entries into a subdirectory, right? If we go with the group level, then
>> we will be moving the existing TSM extra attributes and the new TSM SVSM
>> attributes into new, separate sub-directories.
> 
> I am not following the concern about "losing the grouping"? Here is what
> I was thinking with having the visibility routines in group operations.
> This is just the broard strokes, it compiles, but still needs the finer
> detail work to make tdx-guest skip all the attributes that do not apply
> to it.  Might need to be broken up a bit more, but hopefully conveys the
> idea. Does this address your grouping concern?

Yes and no. Basically the is_visible()/is_bin_visible() callback will 
have to check every index value for a "group" against the passed in 
value. I was trying to group the values together using an enum in order 
to make it a bit easier and more readable in the callback. Adding 
another attribute to the group requires updates in multiple places. But 
thats just how I was looking at it. I can also see where you might want 
to selectively hide/show entries and this method works well for that.

I'll follow this approach (add you as Co-developed-by: or Suggested-by:, 
whichever you prefer) and submit a v4.

Thanks,
Tom

> 
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index 87f241825bc3..39b8455f0ba5 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> @@ -968,7 +968,7 @@ static int __init sev_guest_probe(struct platform_device *pdev)
>   	snp_dev->input.resp_gpa = __pa(snp_dev->response);
>   	snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
>   
> -	ret = tsm_register(&sev_tsm_ops, snp_dev, &tsm_report_extra_type);
> +	ret = tsm_register(&sev_tsm_ops, snp_dev);
>   	if (ret)
>   		goto e_free_cert_data;
>   
> diff --git a/drivers/virt/coco/tdx-guest/tdx-guest.c b/drivers/virt/coco/tdx-guest/tdx-guest.c
> index 1253bf76b570..654d20ea524a 100644
> --- a/drivers/virt/coco/tdx-guest/tdx-guest.c
> +++ b/drivers/virt/coco/tdx-guest/tdx-guest.c
> @@ -301,7 +301,7 @@ static int __init tdx_guest_init(void)
>   		goto free_misc;
>   	}
>   
> -	ret = tsm_register(&tdx_tsm_ops, NULL, NULL);
> +	ret = tsm_register(&tdx_tsm_ops, NULL);
>   	if (ret)
>   		goto free_quote;
>   
> diff --git a/drivers/virt/coco/tsm.c b/drivers/virt/coco/tsm.c
> index d1c2db83a8ca..b31be0e61728 100644
> --- a/drivers/virt/coco/tsm.c
> +++ b/drivers/virt/coco/tsm.c
> @@ -14,7 +14,6 @@
>   
>   static struct tsm_provider {
>   	const struct tsm_ops *ops;
> -	const struct config_item_type *type;
>   	void *data;
>   } provider;
>   static DECLARE_RWSEM(tsm_rwsem);
> @@ -252,34 +251,18 @@ static ssize_t tsm_report_auxblob_read(struct config_item *cfg, void *buf,
>   }
>   CONFIGFS_BIN_ATTR_RO(tsm_report_, auxblob, NULL, TSM_OUTBLOB_MAX);
>   
> -#define TSM_DEFAULT_ATTRS() \
> -	&tsm_report_attr_generation, \
> -	&tsm_report_attr_provider
> -
>   static struct configfs_attribute *tsm_report_attrs[] = {
> -	TSM_DEFAULT_ATTRS(),
> -	NULL,
> -};
> -
> -static struct configfs_attribute *tsm_report_extra_attrs[] = {
> -	TSM_DEFAULT_ATTRS(),
> -	&tsm_report_attr_privlevel,
> -	&tsm_report_attr_privlevel_floor,
> +	[TSM_REPORT_GENERATION] = &tsm_report_attr_generation,
> +	[TSM_REPORT_PROVIDER] = &tsm_report_attr_provider,
> +	[TSM_REPORT_PRIVLEVEL] = &tsm_report_attr_privlevel,
> +	[TSM_REPORT_PRIVLEVEL_FLOOR] = &tsm_report_attr_privlevel_floor,
>   	NULL,
>   };
>   
> -#define TSM_DEFAULT_BIN_ATTRS() \
> -	&tsm_report_attr_inblob, \
> -	&tsm_report_attr_outblob
> -
>   static struct configfs_bin_attribute *tsm_report_bin_attrs[] = {
> -	TSM_DEFAULT_BIN_ATTRS(),
> -	NULL,
> -};
> -
> -static struct configfs_bin_attribute *tsm_report_bin_extra_attrs[] = {
> -	TSM_DEFAULT_BIN_ATTRS(),
> -	&tsm_report_attr_auxblob,
> +	[TSM_REPORT_INBLOB] = &tsm_report_attr_inblob,
> +	[TSM_REPORT_OUTBLOB] = &tsm_report_attr_outblob,
> +	[TSM_REPORT_AUXBLOB] = &tsm_report_attr_auxblob,
>   	NULL,
>   };
>   
> @@ -297,21 +280,12 @@ static struct configfs_item_operations tsm_report_item_ops = {
>   	.release = tsm_report_item_release,
>   };
>   
> -const struct config_item_type tsm_report_default_type = {
> +static const struct config_item_type tsm_report_type = {
>   	.ct_owner = THIS_MODULE,
>   	.ct_bin_attrs = tsm_report_bin_attrs,
>   	.ct_attrs = tsm_report_attrs,
>   	.ct_item_ops = &tsm_report_item_ops,
>   };
> -EXPORT_SYMBOL_GPL(tsm_report_default_type);
> -
> -const struct config_item_type tsm_report_extra_type = {
> -	.ct_owner = THIS_MODULE,
> -	.ct_bin_attrs = tsm_report_bin_extra_attrs,
> -	.ct_attrs = tsm_report_extra_attrs,
> -	.ct_item_ops = &tsm_report_item_ops,
> -};
> -EXPORT_SYMBOL_GPL(tsm_report_extra_type);
>   
>   static struct config_item *tsm_report_make_item(struct config_group *group,
>   						const char *name)
> @@ -326,12 +300,38 @@ static struct config_item *tsm_report_make_item(struct config_group *group,
>   	if (!state)
>   		return ERR_PTR(-ENOMEM);
>   
> -	config_item_init_type_name(&state->cfg, name, provider.type);
> +	config_item_init_type_name(&state->cfg, name, &tsm_report_type);
>   	return &state->cfg;
>   }
>   
> +static bool tsm_report_attr_visible(struct configfs_attribute *attr, int n)
> +{
> +	guard(rwsem_read)(&tsm_rwsem);
> +	if (!provider.ops)
> +		return false;
> +
> +	if (!provider.ops->is_visible)
> +		return true;
> +
> +	return provider.ops->is_visible(n);
> +}
> +
> +static bool tsm_report_bin_attr_visible(struct configfs_bin_attribute *attr,
> +					int n)
> +{
> +	if (!provider.ops)
> +		return false;
> +
> +	if (!provider.ops->is_bin_visible)
> +		return true;
> +
> +	return provider.ops->is_bin_visible(n);
> +}
> +
>   static struct configfs_group_operations tsm_report_group_ops = {
>   	.make_item = tsm_report_make_item,
> +	.is_visible = tsm_report_attr_visible,
> +	.is_bin_visible = tsm_report_bin_attr_visible,
>   };
>   
>   static const struct config_item_type tsm_reports_type = {
> @@ -353,16 +353,10 @@ static struct configfs_subsystem tsm_configfs = {
>   	.su_mutex = __MUTEX_INITIALIZER(tsm_configfs.su_mutex),
>   };
>   
> -int tsm_register(const struct tsm_ops *ops, void *priv,
> -		 const struct config_item_type *type)
> +int tsm_register(const struct tsm_ops *ops, void *priv)
>   {
>   	const struct tsm_ops *conflict;
>   
> -	if (!type)
> -		type = &tsm_report_default_type;
> -	if (!(type == &tsm_report_default_type || type == &tsm_report_extra_type))
> -		return -EINVAL;
> -
>   	guard(rwsem_write)(&tsm_rwsem);
>   	conflict = provider.ops;
>   	if (conflict) {
> @@ -372,7 +366,6 @@ int tsm_register(const struct tsm_ops *ops, void *priv,
>   
>   	provider.ops = ops;
>   	provider.data = priv;
> -	provider.type = type;
>   	return 0;
>   }
>   EXPORT_SYMBOL_GPL(tsm_register);
> @@ -384,7 +377,6 @@ int tsm_unregister(const struct tsm_ops *ops)
>   		return -EBUSY;
>   	provider.ops = NULL;
>   	provider.data = NULL;
> -	provider.type = NULL;
>   	return 0;
>   }
>   EXPORT_SYMBOL_GPL(tsm_unregister);
> diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
> index 18677cd4e62f..213e88f4cec2 100644
> --- a/fs/configfs/dir.c
> +++ b/fs/configfs/dir.c
> @@ -580,6 +580,7 @@ static void detach_attrs(struct config_item * item)
>   static int populate_attrs(struct config_item *item)
>   {
>   	const struct config_item_type *t = item->ci_type;
> +	struct configfs_group_operations *ops = t->ct_group_ops;
>   	struct configfs_attribute *attr;
>   	struct configfs_bin_attribute *bin_attr;
>   	int error = 0;
> @@ -589,12 +590,17 @@ static int populate_attrs(struct config_item *item)
>   		return -EINVAL;
>   	if (t->ct_attrs) {
>   		for (i = 0; (attr = t->ct_attrs[i]) != NULL; i++) {
> +			if (ops && ops->is_visible && !ops->is_visible(attr, i))
> +				continue;
>   			if ((error = configfs_create_file(item, attr)))
>   				break;
>   		}
>   	}
>   	if (t->ct_bin_attrs) {
>   		for (i = 0; (bin_attr = t->ct_bin_attrs[i]) != NULL; i++) {
> +			if (ops && ops->is_bin_visible &&
> +			    !ops->is_bin_visible(bin_attr, i))
> +				continue;
>   			error = configfs_create_bin_file(item, bin_attr);
>   			if (error)
>   				break;
> diff --git a/fs/configfs/file.c b/fs/configfs/file.c
> index 0ad32150611e..356d23b6b9cf 100644
> --- a/fs/configfs/file.c
> +++ b/fs/configfs/file.c
> @@ -444,7 +444,8 @@ const struct file_operations configfs_bin_file_operations = {
>    *	@attr:	atrribute descriptor.
>    */
>   
> -int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
> +int configfs_create_file(struct config_item *item,
> +			 const struct configfs_attribute *attr)
>   {
>   	struct dentry *dir = item->ci_dentry;
>   	struct configfs_dirent *parent_sd = dir->d_fsdata;
> diff --git a/include/linux/configfs.h b/include/linux/configfs.h
> index 2606711adb18..31553f12db7c 100644
> --- a/include/linux/configfs.h
> +++ b/include/linux/configfs.h
> @@ -216,6 +216,8 @@ struct configfs_group_operations {
>   	struct config_group *(*make_group)(struct config_group *group, const char *name);
>   	void (*disconnect_notify)(struct config_group *group, struct config_item *item);
>   	void (*drop_item)(struct config_group *group, struct config_item *item);
> +	bool (*is_visible)(struct configfs_attribute *attr, int n);
> +	bool (*is_bin_visible)(struct configfs_bin_attribute *attr, int n);
>   };
>   
>   struct configfs_subsystem {
> diff --git a/include/linux/tsm.h b/include/linux/tsm.h
> index de8324a2223c..a45b12943223 100644
> --- a/include/linux/tsm.h
> +++ b/include/linux/tsm.h
> @@ -42,6 +42,19 @@ struct tsm_report {
>   	u8 *auxblob;
>   };
>   
> +enum tsm_attr_index {
> +	TSM_REPORT_GENERATION,
> +	TSM_REPORT_PROVIDER,
> +	TSM_REPORT_PRIVLEVEL,
> +	TSM_REPORT_PRIVLEVEL_FLOOR,
> +};
> +
> +enum tsm_bin_attr_index {
> +	TSM_REPORT_INBLOB,
> +	TSM_REPORT_OUTBLOB,
> +	TSM_REPORT_AUXBLOB,
> +};
> +
>   /**
>    * struct tsm_ops - attributes and operations for tsm instances
>    * @name: tsm id reflected in /sys/kernel/config/tsm/report/$report/provider
> @@ -55,15 +68,11 @@ struct tsm_report {
>   struct tsm_ops {
>   	const char *name;
>   	const unsigned int privlevel_floor;
> +	bool (*is_visible)(enum tsm_attr_index index);
> +	bool (*is_bin_visible)(enum tsm_bin_attr_index index);
>   	int (*report_new)(struct tsm_report *report, void *data);
>   };
>   
> -extern const struct config_item_type tsm_report_default_type;
> -
> -/* publish @privlevel, @privlevel_floor, and @auxblob attributes */
> -extern const struct config_item_type tsm_report_extra_type;
> -
> -int tsm_register(const struct tsm_ops *ops, void *priv,
> -		 const struct config_item_type *type);
> +int tsm_register(const struct tsm_ops *ops, void *priv);
>   int tsm_unregister(const struct tsm_ops *ops);
>   #endif /* __TSM_H */