lkml.org 
[lkml]   [2021]   [Dec]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v13 2/2] x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node
From
Date
On Wed, 2021-12-08 at 11:38 -0800, Dave Hansen wrote:
> I reworked the changelog quite a bit, addressing some of Borislav's
> questions. No code changes, though.
>
> The result is below. I've retained Greg's ack. I'll stick this in
> tip/x86/sgx if this looks OK to everyone.
>
> ---
>
> From: Jarkko Sakkinen <jarkko@kernel.org>
>
> == 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>
> Link: https://lkml.kernel.org/r/20211116162116.93081-2-jarkko@kernel.org
> ---
> Documentation/ABI/stable/sysfs-devices-node | 6 ++++++
> arch/Kconfig | 4 ++++
> arch/x86/Kconfig | 1 +
> arch/x86/kernel/cpu/sgx/main.c | 20 ++++++++++++++++++++
> arch/x86/kernel/cpu/sgx/sgx.h | 1 +
> drivers/base/node.c | 3 +++
> include/linux/numa.h | 4 ++++
> 7 files changed, 39 insertions(+)

Thank you! Looks good to me.

/Jarkko

\
 
 \ /
  Last update: 2021-12-11 16:38    [W:0.165 / U:0.236 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site