diff options
| -rw-r--r-- | Documentation/arch/arm64/sme.rst | 4 | ||||
| -rw-r--r-- | arch/arm64/kernel/process.c | 92 |
2 files changed, 64 insertions, 32 deletions
diff --git a/Documentation/arch/arm64/sme.rst b/Documentation/arch/arm64/sme.rst index 3a98aed92732..1c1e48d8bd1a 100644 --- a/Documentation/arch/arm64/sme.rst +++ b/Documentation/arch/arm64/sme.rst @@ -69,8 +69,8 @@ model features for SME is included in Appendix A. vectors from 0 to VL/8-1 stored in the same endianness invariant format as is used for SVE vectors. -* On thread creation TPIDR2_EL0 is preserved unless CLONE_SETTLS is specified, - in which case it is set to 0. +* On thread creation PSTATE.ZA and TPIDR2_EL0 are preserved unless CLONE_VM + is specified, in which case PSTATE.ZA is set to 0 and TPIDR2_EL0 is set to 0. 2. Vector lengths ------------------ diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 27a5b0c7ec60..74bee78cc3fa 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -364,31 +364,14 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) task_smstop_sm(dst); /* - * In the unlikely event that we create a new thread with ZA - * enabled we should retain the ZA and ZT state so duplicate - * it here. This may be shortly freed if we exec() or if - * CLONE_SETTLS but it's simpler to do it here. To avoid - * confusing the rest of the code ensure that we have a - * sve_state allocated whenever sme_state is allocated. + * Drop stale reference to src's sme_state and ensure dst has ZA + * disabled. + * + * When necessary, ZA will be inherited later in copy_thread_za(). */ - if (thread_za_enabled(&src->thread)) { - dst->thread.sve_state = kzalloc(sve_state_size(src), - GFP_KERNEL); - if (!dst->thread.sve_state) - return -ENOMEM; - - dst->thread.sme_state = kmemdup(src->thread.sme_state, - sme_state_size(src), - GFP_KERNEL); - if (!dst->thread.sme_state) { - kfree(dst->thread.sve_state); - dst->thread.sve_state = NULL; - return -ENOMEM; - } - } else { - dst->thread.sme_state = NULL; - clear_tsk_thread_flag(dst, TIF_SME); - } + dst->thread.sme_state = NULL; + clear_tsk_thread_flag(dst, TIF_SME); + dst->thread.svcr &= ~SVCR_ZA_MASK; /* clear any pending asynchronous tag fault raised by the parent */ clear_tsk_thread_flag(dst, TIF_MTE_ASYNC_FAULT); @@ -396,6 +379,31 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) return 0; } +static int copy_thread_za(struct task_struct *dst, struct task_struct *src) +{ + if (!thread_za_enabled(&src->thread)) + return 0; + + dst->thread.sve_state = kzalloc(sve_state_size(src), + GFP_KERNEL); + if (!dst->thread.sve_state) + return -ENOMEM; + + dst->thread.sme_state = kmemdup(src->thread.sme_state, + sme_state_size(src), + GFP_KERNEL); + if (!dst->thread.sme_state) { + kfree(dst->thread.sve_state); + dst->thread.sve_state = NULL; + return -ENOMEM; + } + + set_tsk_thread_flag(dst, TIF_SME); + dst->thread.svcr |= SVCR_ZA_MASK; + + return 0; +} + asmlinkage void ret_from_fork(void) asm("ret_from_fork"); int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) @@ -428,8 +436,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) * out-of-sync with the saved value. */ *task_user_tls(p) = read_sysreg(tpidr_el0); - if (system_supports_tpidr2()) - p->thread.tpidr2_el0 = read_sysreg_s(SYS_TPIDR2_EL0); if (system_supports_poe()) p->thread.por_el0 = read_sysreg_s(SYS_POR_EL0); @@ -442,13 +448,39 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) } /* + * Due to the AAPCS64 "ZA lazy saving scheme", PSTATE.ZA and + * TPIDR2 need to be manipulated as a pair, and either both + * need to be inherited or both need to be reset. + * + * Within a process, child threads must not inherit their + * parent's TPIDR2 value or they may clobber their parent's + * stack at some later point. + * + * When a process is fork()'d, the child must inherit ZA and + * TPIDR2 from its parent in case there was dormant ZA state. + * + * Use CLONE_VM to determine when the child will share the + * address space with the parent, and cannot safely inherit the + * state. + */ + if (system_supports_sme()) { + if (!(clone_flags & CLONE_VM)) { + p->thread.tpidr2_el0 = read_sysreg_s(SYS_TPIDR2_EL0); + ret = copy_thread_za(p, current); + if (ret) + return ret; + } else { + p->thread.tpidr2_el0 = 0; + WARN_ON_ONCE(p->thread.svcr & SVCR_ZA_MASK); + } + } + + /* * If a TLS pointer was passed to clone, use it for the new - * thread. We also reset TPIDR2 if it's in use. + * thread. */ - if (clone_flags & CLONE_SETTLS) { + if (clone_flags & CLONE_SETTLS) p->thread.uw.tp_value = tls; - p->thread.tpidr2_el0 = 0; - } ret = copy_thread_gcs(p, args); if (ret != 0) |