x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node

commit 50468e4313 upstream.

== Problem ==

The amount of SGX memory on a system is determined by the BIOS and it
varies wildly between systems.  It can be as small as dozens of MB's
and as large as many GB's on servers.  Just like how applications need
to know how much regular RAM is available, enclave builders need to
know how much SGX memory an enclave can consume.

== Solution ==

Introduce a new sysfs file:

	/sys/devices/system/node/nodeX/x86/sgx_total_bytes

to enumerate the amount of SGX memory available in each NUMA node.
This serves the same function for SGX as /proc/meminfo or
/sys/devices/system/node/nodeX/meminfo does for normal RAM.

'sgx_total_bytes' is needed today to help drive the SGX selftests.
SGX-specific swap code is exercised by creating overcommitted enclaves
which are larger than the physical SGX memory on the system.  They
currently use a CPUID-based approach which can diverge from the actual
amount of SGX memory available.  'sgx_total_bytes' ensures that the
selftests can work efficiently and do not attempt stupid things like
creating a 100,000 MB enclave on a system with 128 MB of SGX memory.

== Implementation Details ==

Introduce CONFIG_HAVE_ARCH_NODE_DEV_GROUP opt-in flag to expose an
arch specific attribute group, and add an attribute for the amount of
SGX memory in bytes to each NUMA node:

== ABI Design Discussion ==

As opposed to the per-node ABI, a single, global ABI was considered.
However, this would prevent enclaves from being able to size
themselves so that they fit on a single NUMA node.  Essentially, a
single value would rule out NUMA optimizations for enclaves.

Create a new "x86/" directory inside each "nodeX/" sysfs directory.
'sgx_total_bytes' is expected to be the first of at least a few
sgx-specific files to be placed in the new directory.  Just scanning
/proc/meminfo, these are the no-brainers that we have for RAM, but we
need for SGX:

	MemTotal:       xxxx kB // sgx_total_bytes (implemented here)
	MemFree:        yyyy kB // sgx_free_bytes
	SwapTotal:      zzzz kB // sgx_swapped_bytes

So, at *least* three.  I think we will eventually end up needing
something more along the lines of a dozen.  A new directory (as
opposed to being in the nodeX/ "root") directory avoids cluttering the
root with several "sgx_*" files.

Place the new file in a new "nodeX/x86/" directory because SGX is
highly x86-specific.  It is very unlikely that any other architecture
(or even non-Intel x86 vendor) will ever implement SGX.  Using "sgx/"
as opposed to "x86/" was also considered.  But, there is a real chance
this can get used for other arch-specific purposes.

[ dhansen: rewrite changelog ]

Intel-SIG: commit 50468e4313 x86/sgx: Add an attribute for the amount
of SGX memory in a NUMA node.
Backport for SGX EDMM support.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211116162116.93081-2-jarkko@kernel.org
[ Zhiquan:
  This patch adds a new element into array node_dev_groups[],
  however, in 5.4 code the array is defined by macro
  ATTRIBUTE_GROUPS(node_dev).

  Upstream expands this macro at commit 75bd50fa84
  ("drivers/base/node.c: use bin_attribute to break the size limitation
  of cpumap ABI"), it's one of series
  https://lore.kernel.org/all/20210806110251.560-1-song.bao.hua@hisilicon.com
  which involves a lot of additional changes. Unfortunately, this series
  need some fixes that involves more and more dependencies.

  To keep the thing simple, just expand the macro without functional
  changes. ]
Signed-off-by: Zhiquan Li <zhiquan1.li@intel.com>

Documentation/ABI/stable/sysfs-devices-node

@@ -176,3 +176,9 @@ Contact:	Keith Busch <keith.busch@intel.com>
 Description:
 		The cache write policy: 0 for write-back, 1 for write-through,
 		other or unknown.
+
+What:		/sys/devices/system/node/nodeX/x86/sgx_total_bytes
+Date:		November 2021
+Contact:	Jarkko Sakkinen <jarkko@kernel.org>
+Description:
+		The total amount of SGX physical memory in bytes.

arch/Kconfig

@@ -972,6 +972,10 @@ config ARCH_HAS_MEM_ENCRYPT
 config DYNAMIC_SIGFRAME
 	bool
 
+# Select, if arch has a named attribute group bound to NUMA device nodes.
+config HAVE_ARCH_NODE_DEV_GROUP
+	bool
+
 source "kernel/gcov/Kconfig"
 
 source "scripts/gcc-plugins/Kconfig"

arch/x86/Kconfig

@@ -227,6 +227,7 @@ config X86
 	select VIRT_TO_BUS
 	select X86_FEATURE_NAMES		if PROC_FS
 	select PROC_PID_ARCH_STATUS		if PROC_FS
+	select HAVE_ARCH_NODE_DEV_GROUP		if X86_SGX
 
 config INSTRUCTION_DECODER
 	def_bool y

arch/x86/kernel/cpu/sgx/main.c

@@ -825,9 +825,11 @@ static bool __init sgx_page_cache_init(void)
 			INIT_LIST_HEAD(&sgx_numa_nodes[nid].free_page_list);
 			INIT_LIST_HEAD(&sgx_numa_nodes[nid].sgx_poison_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++;
 	}
@@ -901,6 +903,24 @@ int sgx_set_attribute(unsigned long *allowed_attributes,
 }
 EXPORT_SYMBOL_GPL(sgx_set_attribute);
 
+#ifdef CONFIG_NUMA
+static ssize_t sgx_total_bytes_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%lu\n", sgx_numa_nodes[dev->id].size);
+}
+static DEVICE_ATTR_RO(sgx_total_bytes);
+
+static struct attribute *arch_node_dev_attrs[] = {
+	&dev_attr_sgx_total_bytes.attr,
+	NULL,
+};
+
+const struct attribute_group arch_node_dev_group = {
+	.name = "x86",
+	.attrs = arch_node_dev_attrs,
+};
+#endif /* CONFIG_NUMA */
+
 static int __init sgx_init(void)
 {
 	int ret;

arch/x86/kernel/cpu/sgx/sgx.h

@@ -44,6 +44,7 @@ struct sgx_epc_page {
 struct sgx_numa_node {
 	struct list_head free_page_list;
 	struct list_head sgx_poison_page_list;
+	unsigned long size;
 	spinlock_t lock;
 };
 

drivers/base/node.c

@@ -544,7 +544,18 @@ static struct attribute *node_dev_attrs[] = {
 	&dev_attr_vmstat.attr,
 	NULL
 };
-ATTRIBUTE_GROUPS(node_dev);
+
+static const struct attribute_group node_dev_group = {
+	.attrs = node_dev_attrs,
+};
+
+static const struct attribute_group *node_dev_groups[] = {
+	&node_dev_group,
+#ifdef CONFIG_HAVE_ARCH_NODE_DEV_GROUP
+	&arch_node_dev_group,
+#endif
+	NULL
+};
 
 #ifdef CONFIG_HUGETLBFS
 /*

include/linux/numa.h

@@ -41,4 +41,8 @@ static inline int phys_to_target_node(phys_addr_t addr)
 }
 #endif
 
+#ifdef CONFIG_HAVE_ARCH_NODE_DEV_GROUP
+extern const struct attribute_group arch_node_dev_group;
+#endif
+
 #endif /* _LINUX_NUMA_H */