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@xxxxxxxxxx> > > == 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@xxxxxxxxxx> > Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Link: https://lkml.kernel.org/r/20211116162116.93081-2-jarkko@xxxxxxxxxx > --- > 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
