linux/Documentation/ABI/stable/sysfs-devices-node
Jarkko Sakkinen 50468e4313 x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node
== 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 ]

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
2021-12-09 07:02:22 -08:00

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What: /sys/devices/system/node/possible
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
Nodes that could be possibly become online at some point.
What: /sys/devices/system/node/online
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
Nodes that are online.
What: /sys/devices/system/node/has_normal_memory
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
Nodes that have regular memory.
What: /sys/devices/system/node/has_cpu
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
Nodes that have one or more CPUs.
What: /sys/devices/system/node/has_high_memory
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
Nodes that have regular or high memory.
Depends on CONFIG_HIGHMEM.
What: /sys/devices/system/node/nodeX
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
When CONFIG_NUMA is enabled, this is a directory containing
information on node X such as what CPUs are local to the
node. Each file is detailed next.
What: /sys/devices/system/node/nodeX/cpumap
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
The node's cpumap.
What: /sys/devices/system/node/nodeX/cpulist
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
The CPUs associated to the node.
What: /sys/devices/system/node/nodeX/meminfo
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
Provides information about the node's distribution and memory
utilization. Similar to /proc/meminfo, see Documentation/filesystems/proc.rst
What: /sys/devices/system/node/nodeX/numastat
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
The node's hit/miss statistics, in units of pages.
See Documentation/admin-guide/numastat.rst
What: /sys/devices/system/node/nodeX/distance
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
Distance between the node and all the other nodes
in the system.
What: /sys/devices/system/node/nodeX/vmstat
Date: October 2002
Contact: Linux Memory Management list <linux-mm@kvack.org>
Description:
The node's zoned virtual memory statistics.
This is a superset of numastat.
What: /sys/devices/system/node/nodeX/compact
Date: February 2010
Contact: Mel Gorman <mel@csn.ul.ie>
Description:
When this file is written to, all memory within that node
will be compacted. When it completes, memory will be freed
into blocks which have as many contiguous pages as possible
What: /sys/devices/system/node/nodeX/hugepages/hugepages-<size>/
Date: December 2009
Contact: Lee Schermerhorn <lee.schermerhorn@hp.com>
Description:
The node's huge page size control/query attributes.
See Documentation/admin-guide/mm/hugetlbpage.rst
What: /sys/devices/system/node/nodeX/accessY/
Date: December 2018
Contact: Keith Busch <keith.busch@intel.com>
Description:
The node's relationship to other nodes for access class "Y".
What: /sys/devices/system/node/nodeX/accessY/initiators/
Date: December 2018
Contact: Keith Busch <keith.busch@intel.com>
Description:
The directory containing symlinks to memory initiator
nodes that have class "Y" access to this target node's
memory. CPUs and other memory initiators in nodes not in
the list accessing this node's memory may have different
performance.
What: /sys/devices/system/node/nodeX/accessY/targets/
Date: December 2018
Contact: Keith Busch <keith.busch@intel.com>
Description:
The directory containing symlinks to memory targets that
this initiator node has class "Y" access.
What: /sys/devices/system/node/nodeX/accessY/initiators/read_bandwidth
Date: December 2018
Contact: Keith Busch <keith.busch@intel.com>
Description:
This node's read bandwidth in MB/s when accessed from
nodes found in this access class's linked initiators.
What: /sys/devices/system/node/nodeX/accessY/initiators/read_latency
Date: December 2018
Contact: Keith Busch <keith.busch@intel.com>
Description:
This node's read latency in nanoseconds when accessed
from nodes found in this access class's linked initiators.
What: /sys/devices/system/node/nodeX/accessY/initiators/write_bandwidth
Date: December 2018
Contact: Keith Busch <keith.busch@intel.com>
Description:
This node's write bandwidth in MB/s when accessed from
found in this access class's linked initiators.
What: /sys/devices/system/node/nodeX/accessY/initiators/write_latency
Date: December 2018
Contact: Keith Busch <keith.busch@intel.com>
Description:
This node's write latency in nanoseconds when access
from nodes found in this class's linked initiators.
What: /sys/devices/system/node/nodeX/memory_side_cache/indexY/
Date: December 2018
Contact: Keith Busch <keith.busch@intel.com>
Description:
The directory containing attributes for the memory-side cache
level 'Y'.
What: /sys/devices/system/node/nodeX/memory_side_cache/indexY/indexing
Date: December 2018
Contact: Keith Busch <keith.busch@intel.com>
Description:
The caches associativity indexing: 0 for direct mapped,
non-zero if indexed.
What: /sys/devices/system/node/nodeX/memory_side_cache/indexY/line_size
Date: December 2018
Contact: Keith Busch <keith.busch@intel.com>
Description:
The number of bytes accessed from the next cache level on a
cache miss.
What: /sys/devices/system/node/nodeX/memory_side_cache/indexY/size
Date: December 2018
Contact: Keith Busch <keith.busch@intel.com>
Description:
The size of this memory side cache in bytes.
What: /sys/devices/system/node/nodeX/memory_side_cache/indexY/write_policy
Date: December 2018
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.