diff options
| -rw-r--r-- | Documentation/arch/arm64/sme.rst | 2 | ||||
| -rw-r--r-- | arch/arm64/kernel/fpsimd.c | 137 |
2 files changed, 73 insertions, 66 deletions
diff --git a/Documentation/arch/arm64/sme.rst b/Documentation/arch/arm64/sme.rst index 1c1e48d8bd1a..4cb38330e704 100644 --- a/Documentation/arch/arm64/sme.rst +++ b/Documentation/arch/arm64/sme.rst @@ -241,7 +241,7 @@ prctl(PR_SME_SET_VL, unsigned long arg) length, or calling PR_SME_SET_VL with the PR_SME_SET_VL_ONEXEC flag, does not constitute a change to the vector length for this purpose. - * Changing the vector length causes PSTATE.ZA and PSTATE.SM to be cleared. + * Changing the vector length causes PSTATE.ZA to be cleared. Calling PR_SME_SET_VL with vl equal to the thread's current vector length, or calling PR_SME_SET_VL with the PR_SME_SET_VL_ONEXEC flag, does not constitute a change to the vector length for this purpose. diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index faeedaab0558..9c0d1068e7f2 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -724,23 +724,12 @@ void cpu_enable_fpmr(const struct arm64_cpu_capabilities *__always_unused p) } #ifdef CONFIG_ARM64_SVE -/* - * Call __sve_free() directly only if you know task can't be scheduled - * or preempted. - */ -static void __sve_free(struct task_struct *task) +static void sve_free(struct task_struct *task) { kfree(task->thread.sve_state); task->thread.sve_state = NULL; } -static void sve_free(struct task_struct *task) -{ - WARN_ON(test_tsk_thread_flag(task, TIF_SVE)); - - __sve_free(task); -} - /* * Ensure that task->thread.sve_state is allocated and sufficiently large. * @@ -801,10 +790,73 @@ void fpsimd_sync_to_effective_state_zeropad(struct task_struct *task) __fpsimd_to_sve(sst, fst, vq); } +static int change_live_vector_length(struct task_struct *task, + enum vec_type type, + unsigned long vl) +{ + unsigned int sve_vl = task_get_sve_vl(task); + unsigned int sme_vl = task_get_sme_vl(task); + void *sve_state = NULL, *sme_state = NULL; + + if (type == ARM64_VEC_SME) + sme_vl = vl; + else + sve_vl = vl; + + /* + * Allocate the new sve_state and sme_state before freeing the old + * copies so that allocation failure can be handled without needing to + * mutate the task's state in any way. + * + * Changes to the SVE vector length must not discard live ZA state or + * clear PSTATE.ZA, as userspace code which is unaware of the AAPCS64 + * ZA lazy saving scheme may attempt to change the SVE vector length + * while unsaved/dormant ZA state exists. + */ + sve_state = kzalloc(__sve_state_size(sve_vl, sme_vl), GFP_KERNEL); + if (!sve_state) + goto out_mem; + + if (type == ARM64_VEC_SME) { + sme_state = kzalloc(__sme_state_size(sme_vl), GFP_KERNEL); + if (!sme_state) + goto out_mem; + } + + if (task == current) + fpsimd_save_and_flush_current_state(); + else + fpsimd_flush_task_state(task); + + /* + * Always preserve PSTATE.SM and the effective FPSIMD state, zeroing + * other SVE state. + */ + fpsimd_sync_from_effective_state(task); + task_set_vl(task, type, vl); + kfree(task->thread.sve_state); + task->thread.sve_state = sve_state; + fpsimd_sync_to_effective_state_zeropad(task); + + if (type == ARM64_VEC_SME) { + task->thread.svcr &= ~SVCR_ZA_MASK; + kfree(task->thread.sme_state); + task->thread.sme_state = sme_state; + } + + return 0; + +out_mem: + kfree(sve_state); + kfree(sme_state); + return -ENOMEM; +} + int vec_set_vector_length(struct task_struct *task, enum vec_type type, unsigned long vl, unsigned long flags) { - bool free_sme = false; + bool onexec = flags & PR_SVE_SET_VL_ONEXEC; + bool inherit = flags & PR_SVE_VL_INHERIT; if (flags & ~(unsigned long)(PR_SVE_VL_INHERIT | PR_SVE_SET_VL_ONEXEC)) @@ -824,62 +876,17 @@ int vec_set_vector_length(struct task_struct *task, enum vec_type type, vl = find_supported_vector_length(type, vl); - if (flags & (PR_SVE_VL_INHERIT | - PR_SVE_SET_VL_ONEXEC)) + if (!onexec && vl != task_get_vl(task, type)) { + if (change_live_vector_length(task, type, vl)) + return -ENOMEM; + } + + if (onexec || inherit) task_set_vl_onexec(task, type, vl); else /* Reset VL to system default on next exec: */ task_set_vl_onexec(task, type, 0); - /* Only actually set the VL if not deferred: */ - if (flags & PR_SVE_SET_VL_ONEXEC) - goto out; - - if (vl == task_get_vl(task, type)) - goto out; - - /* - * To ensure the FPSIMD bits of the SVE vector registers are preserved, - * write any live register state back to task_struct, and convert to a - * regular FPSIMD thread. - */ - if (task == current) { - get_cpu_fpsimd_context(); - - fpsimd_save_user_state(); - } - - fpsimd_flush_task_state(task); - if (test_and_clear_tsk_thread_flag(task, TIF_SVE) || - thread_sm_enabled(&task->thread)) { - fpsimd_sync_from_effective_state(task); - task->thread.fp_type = FP_STATE_FPSIMD; - } - - if (system_supports_sme() && type == ARM64_VEC_SME) { - task->thread.svcr &= ~(SVCR_SM_MASK | SVCR_ZA_MASK); - clear_tsk_thread_flag(task, TIF_SME); - free_sme = true; - } - - if (task == current) - put_cpu_fpsimd_context(); - - task_set_vl(task, type, vl); - - /* - * Free the changed states if they are not in use, SME will be - * reallocated to the correct size on next use and we just - * allocate SVE now in case it is needed for use in streaming - * mode. - */ - sve_free(task); - sve_alloc(task, true); - - if (free_sme) - sme_free(task); - -out: update_tsk_thread_flag(task, vec_vl_inherit_flag(type), flags & PR_SVE_VL_INHERIT); @@ -1175,7 +1182,7 @@ void __init sve_setup(void) */ void fpsimd_release_task(struct task_struct *dead_task) { - __sve_free(dead_task); + sve_free(dead_task); sme_free(dead_task); } |