Re: [PATCH V2 03/15] x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node
From: Reinette Chatre
Date: Fri Oct 29 2021 - 15:03:43 EST
Hi Dave,
On 10/29/2021 11:06 AM, Dave Hansen wrote:
On 10/28/21 1:37 PM, Reinette Chatre 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.
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.
For now, can we just make the selftests read the SGX CPUID section
leaves? It's not as precise as knowing how much the kernel actually
decided to use, but it's good enough for a selftest. It also means we
can merge something without having to worry about long-term ABI.
Yes, we can do that.
This is also why I once suggested that we first make the selftests
depend on some debugfs file that would be short-lived. But, if we use
CPUID, we don't even need to mess with debugfs.
My apologies, this was not intended to avoid your suggestion. V1 did use
the debugfs solution as you suggested as placeholder but after the
debufs solution evolved the tests were adapted to follow those changes
instead of sticking with the debugfs solution as proposed in
https://lore.kernel.org/lkml/6f3cc681e10877e639b882eaabf1a5e21bd2fc94.camel@xxxxxxxxxx/
You can even just steal the code from sgx_page_cache_init() to do it.
Would that work, or am I missing something?
I do think that will work. The selftests are only interested in the
total SGX memory (as opposed to memory per numa node as exposed with the
current interface) and that can be obtained via CPUID. I will adapt the
oversubscription test case to obtain its needed info via CPUID.
Thank you very much
Reinette