diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c index 7ad8b475306a..6953d331f8d5 100644 --- a/arch/x86/kernel/cpu/sgx/encl.c +++ b/arch/x86/kernel/cpu/sgx/encl.c @@ -714,6 +714,73 @@ int sgx_encl_mm_add(struct sgx_encl *encl, struct mm_struct *mm) return 0; } +/** + * sgx_encl_ewb_cpumask() - Query which CPUs might be accessing the enclave + * @encl: the enclave + * + * Some SGX functions require that no cached linear-to-physical address + * mappings are present before they can succeed. For example, ENCLS[EWB] + * copies a page from the enclave page cache to regular main memory but + * it fails if it cannot ensure that there are no cached + * linear-to-physical address mappings referring to the page. + * + * SGX hardware flushes all cached linear-to-physical mappings on a CPU + * when an enclave is exited via ENCLU[EEXIT] or an Asynchronous Enclave + * Exit (AEX). Exiting an enclave will thus ensure cached linear-to-physical + * address mappings are cleared but coordination with the tracking done within + * the SGX hardware is needed to support the SGX functions that depend on this + * cache clearing. + * + * When the ENCLS[ETRACK] function is issued on an enclave the hardware + * tracks threads operating inside the enclave at that time. The SGX + * hardware tracking require that all the identified threads must have + * exited the enclave in order to flush the mappings before a function such + * as ENCLS[EWB] will be permitted + * + * The following flow is used to support SGX functions that require that + * no cached linear-to-physical address mappings are present: + * 1) Execute ENCLS[ETRACK] to initiate hardware tracking. + * 2) Use this function (sgx_encl_ewb_cpumask()) to query which CPUs might be + * accessing the enclave. + * 3) Send IPI to identified CPUs, kicking them out of the enclave and + * thus flushing all locally cached linear-to-physical address mappings. + * 4) Execute SGX function. + * + * Context: It is required to call this function after ENCLS[ETRACK]. + * This will ensure that if any new mm appears (racing with + * sgx_encl_mm_add()) then the new mm will enter into the + * enclave with fresh linear-to-physical address mappings. + * + * It is required that all IPIs are completed before a new + * ENCLS[ETRACK] is issued so be sure to protect steps 1 to 3 + * of the above flow with the enclave's mutex. + * + * Return: cpumask of CPUs that might be accessing @encl + */ +const cpumask_t *sgx_encl_ewb_cpumask(struct sgx_encl *encl) +{ + cpumask_t *cpumask = &encl->cpumask; + struct sgx_encl_mm *encl_mm; + int idx; + + cpumask_clear(cpumask); + + idx = srcu_read_lock(&encl->srcu); + + list_for_each_entry_rcu(encl_mm, &encl->mm_list, list) { + if (!mmget_not_zero(encl_mm->mm)) + continue; + + cpumask_or(cpumask, cpumask, mm_cpumask(encl_mm->mm)); + + mmput_async(encl_mm->mm); + } + + srcu_read_unlock(&encl->srcu, idx); + + return cpumask; +} + static struct page *sgx_encl_get_backing_page(struct sgx_encl *encl, pgoff_t index) { diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h index 522a17e4fd2d..c6afa58ea3e6 100644 --- a/arch/x86/kernel/cpu/sgx/encl.h +++ b/arch/x86/kernel/cpu/sgx/encl.h @@ -105,6 +105,7 @@ int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start, void sgx_encl_release(struct kref *ref); int sgx_encl_mm_add(struct sgx_encl *encl, struct mm_struct *mm); +const cpumask_t *sgx_encl_ewb_cpumask(struct sgx_encl *encl); int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index, struct sgx_backing *backing); void sgx_encl_put_backing(struct sgx_backing *backing); diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c index ab4ec54bbdd9..2a926278dd29 100644 --- a/arch/x86/kernel/cpu/sgx/main.c +++ b/arch/x86/kernel/cpu/sgx/main.c @@ -205,35 +205,6 @@ static void sgx_ipi_cb(void *info) { } -static const cpumask_t *sgx_encl_ewb_cpumask(struct sgx_encl *encl) -{ - cpumask_t *cpumask = &encl->cpumask; - struct sgx_encl_mm *encl_mm; - int idx; - - /* - * Can race with sgx_encl_mm_add(), but ETRACK has already been - * executed, which means that the CPUs running in the new mm will enter - * into the enclave with a fresh epoch. - */ - cpumask_clear(cpumask); - - idx = srcu_read_lock(&encl->srcu); - - list_for_each_entry_rcu(encl_mm, &encl->mm_list, list) { - if (!mmget_not_zero(encl_mm->mm)) - continue; - - cpumask_or(cpumask, cpumask, mm_cpumask(encl_mm->mm)); - - mmput_async(encl_mm->mm); - } - - srcu_read_unlock(&encl->srcu, idx); - - return cpumask; -} - /* * Swap page to the regular memory transformed to the blocked state by using * EBLOCK, which means that it can no longer be referenced (no new TLB entries).