SGX currently allows EPC pages to be overcommitted. If the system is out of enclave memory, EPC pages are swapped to normal RAM via a per enclave shared memory area. This shared memory is not charged to the enclave or the task mapping it, making it hard to account for using normal methods. Since SGX will allow EPC pages to be overcommitted without limits, enclaves can consume system memory for these backing pages without limits. In order to prevent this, set a cap on the amount of overcommit SGX allows. Whenever a backing page is requested by an enclave, track the total amount of shared memory pages used across all enclaves and return an error if the overcommit limit has been reached. This will restrict the total amount of backing pages that all enclaves can consume to a maximum amount, and prevent enclaves from consuming all the system RAM for backing pages. The overcommit percentage has a value of 150, which limits shared memory page consumption to 1.5x the number of EPC pages in the system. Changes from v2 --------------- * whitespace change * use reverse christmas tree format for variable * modify commit message to add information about user impact Changes from v1 ---------------- * removed module parameter and disable boolean * increased over commit percentage to 150% from 100% Kristen Carlson Accardi (2): x86/sgx: Add accounting for tracking overcommit x86/sgx: account backing pages arch/x86/kernel/cpu/sgx/encl.c | 76 ++++++++++++++++++++++++++++++++-- arch/x86/kernel/cpu/sgx/encl.h | 6 ++- arch/x86/kernel/cpu/sgx/main.c | 52 +++++++++++++++++++++-- arch/x86/kernel/cpu/sgx/sgx.h | 2 + 4 files changed, 128 insertions(+), 8 deletions(-) -- 2.20.1 Kristen Carlson Accardi (2): x86/sgx: Add accounting for tracking overcommit x86/sgx: account backing pages arch/x86/kernel/cpu/sgx/encl.c | 76 ++++++++++++++++++++++++++++++++-- arch/x86/kernel/cpu/sgx/encl.h | 6 ++- arch/x86/kernel/cpu/sgx/main.c | 51 +++++++++++++++++++++-- arch/x86/kernel/cpu/sgx/sgx.h | 2 + 4 files changed, 127 insertions(+), 8 deletions(-) -- 2.20.1
