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.
