x86/sgx: Rename fallback labels in sgx_init()

The amount of SGX memory on the system is determined by the BIOS and it varies wildly between systems. It can be from dozens of MB's on desktops or VM's, up to many GB's on servers. Just like for regular memory, it is sometimes useful to know the amount of usable SGX memory in the system.

Add an attribute for the amount of SGX memory in bytes to each NUMA node. The path is /sys/devices/system/node/node[0-9]*/sgx/size. Calculate these values by summing up EPC section sizes for each node during the driver initalization.

Cc Greg Kroah-Hartman <[email protected]>

Signed-off-by Jarkko Sakkinen <[email protected]>

---
v8:
* Fix a bug in sgx_numa_init(): node->dev should be only set after sysfe_create_group(). Otherwise, sysfs_remove_group() will issue a warning in sgx_numa_exit(), when sgx_create_group() is unsuccessful, because the group does not exist.

v7:
* Shorten memory_size to size. The prefix makes the name only longer but does not clarify things more than "size" would.
* Use device_attribute instead of kobj_attribute.
* Use named attribute group instead of creating raw kobject just for the "sgx" subdirectory.

v6:
* Initialize node->size to zero in sgx_setup_epc_section(), when the node is first accessed.

v5
* A new patch based on the discussion on
https://lore.kernel.org/linux-sgx/[email protected]/T/#t

---
 Documentation/ABI/stable/sysfs-devices-node |  7 ++
 arch/x86/kernel/cpu/sgx/main.c              | 85 +++++++++++++++++++++
 arch/x86/kernel/cpu/sgx/sgx.h               |  2 +
 3 files changed, 94 insertions(+)

Documentation/ABI/stable/sysfs-devices-node +7 -0

index 484fc04bcc25..12dc2149e8e0 100644
@@ -176,3 +176,10 @@ Contact:	Keith Busch <[email protected]>
 Description:
 		The cache write policy: 0 for write-back, 1 for write-through,
 		other or unknown.
+
+What:		/sys/devices/system/node/nodeX/sgx/size
+Date:		October 2021
+Contact:	Jarkko Sakkinen <[email protected]>
+Description:
+		Total available physical SGX memory, also known as Enclave Page
+		Cache (EPC), in bytes.

arch/x86/kernel/cpu/sgx/main.c +46 -0

index a6e313f1a82d..dc1d46c51323 100644
@@ -714,9 +714,11 @@ static bool __init sgx_page_cache_init(void)
 			spin_lock_init(&sgx_numa_nodes[nid].lock);
 			INIT_LIST_HEAD(&sgx_numa_nodes[nid].free_page_list);
 			node_set(nid, sgx_numa_mask);
+			sgx_numa_nodes[nid].size = 0;
 		}
 
 		sgx_epc_sections[i].node =  &sgx_numa_nodes[nid];
+		sgx_numa_nodes[nid].size += size;
 
 		sgx_nr_epc_sections++;
 	}

@@ -790,6 +792,81 @@ int sgx_set_attribute(unsigned long *allowed_attributes,
 }
 EXPORT_SYMBOL_GPL(sgx_set_attribute);
 
+#ifdef CONFIG_NUMA
+static ssize_t size_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	unsigned long size = 0;
+	int nid;
+
+	for (nid = 0; nid < num_possible_nodes(); nid++) {
+		if (dev == sgx_numa_nodes[nid].dev) {
+			size = sgx_numa_nodes[nid].size;
+			break;
+		}
+	}
+
+	return sysfs_emit(buf, "%lu\n", size);
+}
+DEVICE_ATTR_RO(size);
+
+static struct attribute *sgx_node_attrs[] = {
+	&dev_attr_size.attr,
+	NULL,
+};
+
+static const struct attribute_group sgx_node_attr_group = {
+	.name = "sgx",
+	.attrs = sgx_node_attrs,
+};
+
+static void sgx_numa_exit(void)
+{
+	struct device *dev;
+	int nid;
+
+	for (nid = 0; nid < num_possible_nodes(); nid++) {
+		dev = &node_devices[nid]->dev;
+		if (dev)
+			sysfs_remove_group(&dev->kobj, &sgx_node_attr_group);
+	}
+}
+
+static bool sgx_numa_init(void)
+{
+	struct sgx_numa_node *node;
+	struct device *dev;
+	int nid;

Quoted 1 line

+               ret = sysfs_create_group(&dev->kobj, &sgx_node_attr_group);

A huge hint, if a driver has to call a sysfs_* call, something is wrong.

Something is wrong here.

Why are you messing around with a kobject?  This is a device, that you control, you can just set the default attribute group for it and then the driver core will add and remove the sysfs group at the proper time, in the proper way.  Right now you are racing userspace and loosing.

Use the default group list, that is what it is there for.

Quoted 11 lines · Greg Kroah-Hartman

Quoted 1 line

+               ret = sysfs_create_group(&dev->kobj, &sgx_node_attr_group);

A huge hint, if a driver has to call a sysfs_* call, something is wrong.

Something is wrong here.

Why are you messing around with a kobject?  This is a device, that you control, you can just set the default attribute group for it and then the driver core will add and remove the sysfs group at the proper time, in the proper way.  Right now you are racing userspace and loosing.

Quoted 1 line

Use the default group list, that is what it is there for.

I used sysfs_create_group() because node_devices is not owned by SGX code. It is managed in drivers/base/node.c, and also initialized before SGX.

Quoted 12 lines · Jarkko Sakkinen

Quoted 11 lines · Greg Kroah-Hartman

Quoted 1 line

+               ret = sysfs_create_group(&dev->kobj, &sgx_node_attr_group);

A huge hint, if a driver has to call a sysfs_* call, something is wrong.

Something is wrong here.

Why are you messing around with a kobject?  This is a device, that you control, you can just set the default attribute group for it and then the driver core will add and remove the sysfs group at the proper time, in the proper way.  Right now you are racing userspace and loosing.

Quoted 5 lines

Quoted 1 line

Use the default group list, that is what it is there for.

I used sysfs_create_group() because node_devices is not owned by SGX code. It is managed in drivers/base/node.c, and also initialized before SGX.

Then that is broken, please do not use that device as your code does not "own" it.  Or fix the logic to be initialized earlier.

thanks,

greg k-h

Quoted 13 lines · Greg Kroah-Hartman

Quoted 12 lines · Jarkko Sakkinen

Quoted 11 lines · Greg Kroah-Hartman

Quoted 1 line

+               ret = sysfs_create_group(&dev->kobj, &sgx_node_attr_group);

A huge hint, if a driver has to call a sysfs_* call, something is wrong.

Something is wrong here.

Why are you messing around with a kobject?  This is a device, that you control, you can just set the default attribute group for it and then the driver core will add and remove the sysfs group at the proper time, in the proper way.  Right now you are racing userspace and loosing.

Quoted 8 lines

Quoted 5 lines

Quoted 1 line

Use the default group list, that is what it is there for.

I used sysfs_create_group() because node_devices is not owned by SGX code. It is managed in drivers/base/node.c, and also initialized before SGX.

Then that is broken, please do not use that device as your code does not "own" it.  Or fix the logic to be initialized earlier.

To get a synchronous initialization, I'd need to add the attributes as part of this declaration:

static struct attribute *node_dev_attrs[] = {
&dev_attr_cpumap.attr,
&dev_attr_cpulist.attr,
&dev_attr_meminfo.attr,
&dev_attr_numastat.attr,
&dev_attr_distance.attr,
&dev_attr_vmstat.attr,
NULL
};
ATTRIBUTE_GROUPS(node_dev);

That guarantees that the attribute exists at the time when the node is created, e.g. in that sense this will fix the race with uevent code.

However, up until sgx_init() has been completed, the attribute will emit '0'.

If I change sgx_init() from device_initcall() to core_initcall() (i.e. one before postcore_initcall(), can I expect these to work:

* node_isset()
* node_set()
* num_possibles_nodes()
* numa_node_id()
* next_node_in()

?

Quoted 41 lines · Jarkko Sakkinen

Quoted 13 lines · Greg Kroah-Hartman

Quoted 12 lines · Jarkko Sakkinen

Quoted 11 lines · Greg Kroah-Hartman

Quoted 1 line

+               ret = sysfs_create_group(&dev->kobj, &sgx_node_attr_group);

A huge hint, if a driver has to call a sysfs_* call, something is wrong.

Something is wrong here.

Why are you messing around with a kobject?  This is a device, that you control, you can just set the default attribute group for it and then the driver core will add and remove the sysfs group at the proper time, in the proper way.  Right now you are racing userspace and loosing.

Quoted 8 lines

Quoted 5 lines

Quoted 1 line

Use the default group list, that is what it is there for.

I used sysfs_create_group() because node_devices is not owned by SGX code. It is managed in drivers/base/node.c, and also initialized before SGX.

Then that is broken, please do not use that device as your code does not "own" it.  Or fix the logic to be initialized earlier.

To get a synchronous initialization, I'd need to add the attributes as part of this declaration:

static struct attribute *node_dev_attrs[] = {
        &dev_attr_cpumap.attr,
        &dev_attr_cpulist.attr,
        &dev_attr_meminfo.attr,
        &dev_attr_numastat.attr,
        &dev_attr_distance.attr,
        &dev_attr_vmstat.attr,
        NULL
};
ATTRIBUTE_GROUPS(node_dev);

That guarantees that the attribute exists at the time when the node is created, e.g. in that sense this will fix the race with uevent code.

Quoted 2 lines

However, up until sgx_init() has been completed, the attribute will emit '0'.

Is that a problem?  Who would be wanting to use sgx until that happens? You have this issue today anyway, right?