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From: Dave Hansen <>
To: Jarkko Sakkinen <>,
	Thomas Gleixner <>,
	Ingo Molnar <>, Borislav Petkov <>,
	Dave Hansen <>,, "H. Peter Anvin" <>,
	Greg Kroah-Hartman <>,
	"Rafael J. Wysocki" <>
Subject: Re: [PATCH v13 2/2] x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node
Date: Tue, 7 Dec 2021 11:36:50 -0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 11/16/21 8:21 AM, Jarkko Sakkinen wrote:
> 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.
> 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:
> /sys/devices/system/node/nodeX/x86/sgx_total_bytes

There's some context missing here:

This serves the same function for SGX memory as /proc/meminfo or
/sys/devices/system/node/nodeX/meminfo does for normal RAM.  It
enumerates how much physical SGX memory is present so that you can size
enclaves on different systems.

This specific file (sgx_total_bytes) is needed today to help drive the
SGX selftests.  The SGX selftests need to create 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.  This file 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.

The nodeX/x86 directory is used because SGX is highly x86-specific.
It's very unlikely that any other architecture (or even non-Intel x86
vendor) will ever implement SGX.  It needs its own directory (as opposed
to being in the nodeX/ "root") because this is expected to be the first
of a few different things that need to get exported.  This avoids
cluttering the root with several "sgx_*" files.

How many of these files will there be?  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 (this patch)
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.

  parent reply	other threads:[~2021-12-07 19:37 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-16 16:21 [PATCH v13 1/2] x86/sgx: Rename fallback labels in sgx_init() Jarkko Sakkinen
2021-11-16 16:21 ` [PATCH v13 2/2] x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node Jarkko Sakkinen
2021-12-04 23:51   ` Jarkko Sakkinen
2021-12-07 19:36   ` Dave Hansen [this message]
2021-12-08 10:10     ` Borislav Petkov
2021-12-08 19:38       ` Dave Hansen
2021-12-09 12:08         ` Borislav Petkov
2021-12-11 15:37         ` Jarkko Sakkinen
2021-12-11 15:36     ` Jarkko Sakkinen
2021-12-09 15:35   ` [tip: x86/sgx] " tip-bot2 for Jarkko Sakkinen
2021-12-17 19:12   ` [PATCH v13 2/2] " Nathan Chancellor
2021-12-17 21:17     ` Dave Hansen
2021-12-17 22:04       ` Nathan Chancellor
2021-12-28 23:45     ` Jarkko Sakkinen
2022-01-02  4:54       ` Dave Hansen
2022-01-02 23:20         ` Nathan Chancellor
2022-01-04 16:52         ` Dave Hansen
2022-01-06 19:18         ` Jarkko Sakkinen
2022-01-07 11:42           ` Jarkko Sakkinen

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